diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/rcu.h | 21 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 17 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 17 | ||||
| -rw-r--r-- | kernel/rcu/rcuperf.c | 27 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 59 | ||||
| -rw-r--r-- | kernel/rcu/srcutiny.c | 17 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 72 | ||||
| -rw-r--r-- | kernel/rcu/sync.c | 15 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 19 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 267 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 53 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 201 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 238 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 17 |
14 files changed, 390 insertions, 650 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index a393e24a9195..acee72c0b24b 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -1,23 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update definitions shared among RCU implementations. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2011 * - * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Author: Paul E. McKenney <paulmck@linux.ibm.com> */ #ifndef __LINUX_RCU_H @@ -30,7 +17,7 @@ #define RCU_TRACE(stmt) #endif /* #else #ifdef CONFIG_RCU_TRACE */ -/* Offset to allow for unmatched rcu_irq_{enter,exit}(). */ +/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */ #define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1) @@ -462,8 +449,6 @@ void rcu_request_urgent_qs_task(struct task_struct *t); enum rcutorture_type { RCU_FLAVOR, - RCU_BH_FLAVOR, - RCU_SCHED_FLAVOR, RCU_TASKS_FLAVOR, SRCU_FLAVOR, INVALID_RCU_FLAVOR diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 5aff271adf1e..9bd5f6023c21 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * RCU segmented callback lists, function definitions * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2017 * - * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ #include <linux/types.h> diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index 948470cef385..71b64648464e 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -1,23 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * RCU segmented callback lists, internal-to-rcu header file * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2017 * - * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ #include <linux/rcu_segcblist.h> diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index b459da70b4fc..c29761152874 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update module-based performance-test facility * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2015 * - * Authors: Paul E. McKenney <paulmck@us.ibm.com> + * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ #define pr_fmt(fmt) fmt @@ -54,7 +41,7 @@ #include "rcu.h" MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); +MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>"); #define PERF_FLAG "-perf:" #define PERFOUT_STRING(s) \ @@ -83,13 +70,19 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); * Various other use cases may of course be specified. */ +#ifdef MODULE +# define RCUPERF_SHUTDOWN 0 +#else +# define RCUPERF_SHUTDOWN 1 +#endif + torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives"); torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader"); torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); torture_param(int, holdoff, 10, "Holdoff time before test start (s)"); torture_param(int, nreaders, -1, "Number of RCU reader threads"); torture_param(int, nwriters, -1, "Number of RCU updater threads"); -torture_param(bool, shutdown, !IS_ENABLED(MODULE), +torture_param(bool, shutdown, RCUPERF_SHUTDOWN, "Shutdown at end of performance tests."); torture_param(int, verbose, 1, "Enable verbose debugging printk()s"); torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable"); diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index f6e85faa4ff4..f14d1b18a74f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update module-based torture test facility * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2005, 2006 * - * Authors: Paul E. McKenney <paulmck@us.ibm.com> + * Authors: Paul E. McKenney <paulmck@linux.ibm.com> * Josh Triplett <josh@joshtriplett.org> * * See also: Documentation/RCU/torture.txt @@ -61,7 +48,7 @@ #include "rcu.h" MODULE_LICENSE("GPL"); -MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>"); +MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>"); /* Bits for ->extendables field, extendables param, and related definitions. */ @@ -1630,21 +1617,34 @@ static bool rcu_fwd_emergency_stop; #define MIN_FWD_CB_LAUNDERS 3 /* This many CB invocations to count. */ #define MIN_FWD_CBS_LAUNDERED 100 /* Number of counted CBs. */ #define FWD_CBS_HIST_DIV 10 /* Histogram buckets/second. */ -static long n_launders_hist[2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV)]; +struct rcu_launder_hist { + long n_launders; + unsigned long launder_gp_seq; +}; +#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV)) +static struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST]; +static unsigned long rcu_launder_gp_seq_start; static void rcu_torture_fwd_cb_hist(void) { + unsigned long gps; + unsigned long gps_old; int i; int j; for (i = ARRAY_SIZE(n_launders_hist) - 1; i > 0; i--) - if (n_launders_hist[i] > 0) + if (n_launders_hist[i].n_launders > 0) break; pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):", __func__, jiffies - rcu_fwd_startat); - for (j = 0; j <= i; j++) - pr_cont(" %ds/%d: %ld", - j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j]); + gps_old = rcu_launder_gp_seq_start; + for (j = 0; j <= i; j++) { + gps = n_launders_hist[j].launder_gp_seq; + pr_cont(" %ds/%d: %ld:%ld", + j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j].n_launders, + rcutorture_seq_diff(gps, gps_old)); + gps_old = gps; + } pr_cont("\n"); } @@ -1666,7 +1666,8 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); if (i >= ARRAY_SIZE(n_launders_hist)) i = ARRAY_SIZE(n_launders_hist) - 1; - n_launders_hist[i]++; + n_launders_hist[i].n_launders++; + n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq(); spin_unlock_irqrestore(&rcu_fwd_lock, flags); } @@ -1786,9 +1787,10 @@ static void rcu_torture_fwd_prog_cr(void) n_max_cbs = 0; n_max_gps = 0; for (i = 0; i < ARRAY_SIZE(n_launders_hist); i++) - n_launders_hist[i] = 0; + n_launders_hist[i].n_launders = 0; cver = READ_ONCE(rcu_torture_current_version); gps = cur_ops->get_gp_seq(); + rcu_launder_gp_seq_start = gps; while (time_before(jiffies, stopat) && !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) { rfcp = READ_ONCE(rcu_fwd_cb_head); @@ -2228,6 +2230,14 @@ static void rcu_test_debug_objects(void) #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ } +static void rcutorture_sync(void) +{ + static unsigned long n; + + if (cur_ops->sync && !(++n & 0xfff)) + cur_ops->sync(); +} + static int __init rcu_torture_init(void) { @@ -2389,7 +2399,8 @@ rcu_torture_init(void) firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup); if (firsterr) goto unwind; - firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval); + firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, + rcutorture_sync); if (firsterr) goto unwind; firsterr = rcu_torture_stall_init(); diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 32dfd6522548..5d4a39a6505a 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -1,24 +1,11 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Sleepable Read-Copy Update mechanism for mutual exclusion, * tiny version for non-preemptible single-CPU use. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2017 * - * Author: Paul McKenney <paulmck@us.ibm.com> + * Author: Paul McKenney <paulmck@linux.ibm.com> */ #include <linux/export.h> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 3600d88d8956..a60b8ba9e1ac 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1,24 +1,11 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Sleepable Read-Copy Update mechanism for mutual exclusion. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (C) IBM Corporation, 2006 * Copyright (C) Fujitsu, 2012 * - * Author: Paul McKenney <paulmck@us.ibm.com> + * Author: Paul McKenney <paulmck@linux.ibm.com> * Lai Jiangshan <laijs@cn.fujitsu.com> * * For detailed explanation of Read-Copy Update mechanism see - @@ -58,6 +45,7 @@ static bool __read_mostly srcu_init_done; static void srcu_invoke_callbacks(struct work_struct *work); static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay); static void process_srcu(struct work_struct *work); +static void srcu_delay_timer(struct timer_list *t); /* Wrappers for lock acquisition and release, see raw_spin_lock_rcu_node(). */ #define spin_lock_rcu_node(p) \ @@ -156,7 +144,8 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static) snp->grphi = cpu; } sdp->cpu = cpu; - INIT_DELAYED_WORK(&sdp->work, srcu_invoke_callbacks); + INIT_WORK(&sdp->work, srcu_invoke_callbacks); + timer_setup(&sdp->delay_work, srcu_delay_timer, 0); sdp->ssp = ssp; sdp->grpmask = 1 << (cpu - sdp->mynode->grplo); if (is_static) @@ -386,13 +375,19 @@ void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced) } else { flush_delayed_work(&ssp->work); } - for_each_possible_cpu(cpu) + for_each_possible_cpu(cpu) { + struct srcu_data *sdp = per_cpu_ptr(ssp->sda, cpu); + if (quiesced) { - if (WARN_ON(delayed_work_pending(&per_cpu_ptr(ssp->sda, cpu)->work))) + if (WARN_ON(timer_pending(&sdp->delay_work))) + return; /* Just leak it! */ + if (WARN_ON(work_pending(&sdp->work))) return; /* Just leak it! */ } else { - flush_delayed_work(&per_cpu_ptr(ssp->sda, cpu)->work); + del_timer_sync(&sdp->delay_work); + flush_work(&sdp->work); } + } if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) || WARN_ON(srcu_readers_active(ssp))) { pr_info("%s: Active srcu_struct %p state: %d\n", @@ -463,39 +458,23 @@ static void srcu_gp_start(struct srcu_struct *ssp) WARN_ON_ONCE(state != SRCU_STATE_SCAN1); } -/* - * Track online CPUs to guide callback workqueue placement. - */ -DEFINE_PER_CPU(bool, srcu_online); -void srcu_online_cpu(unsigned int cpu) +static void srcu_delay_timer(struct timer_list *t) { - WRITE_ONCE(per_cpu(srcu_online, cpu), true); -} + struct srcu_data *sdp = container_of(t, struct srcu_data, delay_work); -void srcu_offline_cpu(unsigned int cpu) -{ - WRITE_ONCE(per_cpu(srcu_online, cpu), false); + queue_work_on(sdp->cpu, rcu_gp_wq, &sdp->work); } -/* - * Place the workqueue handler on the specified CPU if online, otherwise - * just run it whereever. This is useful for placing workqueue handlers - * that are to invoke the specified CPU's callbacks. - */ -static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, - struct delayed_work *dwork, +static void srcu_queue_delayed_work_on(struct srcu_data *sdp, unsigned long delay) { - bool ret; + if (!delay) { + queue_work_on(sdp->cpu, rcu_gp_wq, &sdp->work); + return; + } - preempt_disable(); - if (READ_ONCE(per_cpu(srcu_online, cpu))) - ret = queue_delayed_work_on(cpu, wq, dwork, delay); - else - ret = queue_delayed_work(wq, dwork, delay); - preempt_enable(); - return ret; + timer_reduce(&sdp->delay_work, jiffies + delay); } /* @@ -504,7 +483,7 @@ static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq, */ static void srcu_schedule_cbs_sdp(struct srcu_data *sdp, unsigned long delay) { - srcu_queue_delayed_work_on(sdp->cpu, rcu_gp_wq, &sdp->work, delay); + srcu_queue_delayed_work_on(sdp, delay); } /* @@ -1186,7 +1165,8 @@ static void srcu_invoke_callbacks(struct work_struct *work) struct srcu_data *sdp; struct srcu_struct *ssp; - sdp = container_of(work, struct srcu_data, work.work); + sdp = container_of(work, struct srcu_data, work); + ssp = sdp->ssp; rcu_cblist_init(&ready_cbs); spin_lock_irq_rcu_node(sdp); diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index be10036fa621..a8304d90573f 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -1,20 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * RCU-based infrastructure for lightweight reader-writer locking * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright (c) 2015, Red Hat, Inc. * * Author: Oleg Nesterov <oleg@redhat.com> diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 5f5963ba313e..911bd9076d43 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -1,23 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * - * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Author: Paul E. McKenney <paulmck@linux.ibm.com> * * For detailed explanation of Read-Copy Update mechanism see - * Documentation/RCU @@ -76,7 +63,7 @@ void rcu_qs(void) * be called from hardirq context. It is normally called from the * scheduling-clock interrupt. */ -void rcu_check_callbacks(int user) +void rcu_sched_clock_irq(int user) { if (user) { rcu_qs(); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9180158756d2..3b084dbfb4bc 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1,27 +1,14 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> * Manfred Spraul <manfred@colorfullife.com> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version + * Paul E. McKenney <paulmck@linux.ibm.com> Hierarchical version * - * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * Based on the original work by Paul McKenney <paulmck@linux.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * * For detailed explanation of Read-Copy Update mechanism see - @@ -62,6 +49,7 @@ #include <linux/suspend.h> #include <linux/ftrace.h> #include <linux/tick.h> +#include <linux/sysrq.h> #include "tree.h" #include "rcu.h" @@ -115,6 +103,9 @@ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ /* panic() on RCU Stall sysctl. */ int sysctl_panic_on_rcu_stall __read_mostly; +/* Commandeer a sysrq key to dump RCU's tree. */ +static bool sysrq_rcu; +module_param(sysrq_rcu, bool, 0444); /* * The rcu_scheduler_active variable is initialized to the value @@ -479,7 +470,6 @@ module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next module_param(rcu_kick_kthreads, bool, 0644); static void force_qs_rnp(int (*f)(struct rcu_data *rdp)); -static void force_quiescent_state(void); static int rcu_pending(void); /* @@ -504,13 +494,12 @@ unsigned long rcu_exp_batches_completed(void) EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); /* - * Force a quiescent state. + * Return the root node of the rcu_state structure. */ -void rcu_force_quiescent_state(void) +static struct rcu_node *rcu_get_root(void) { - force_quiescent_state(); + return &rcu_state.node[0]; } -EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* * Convert a ->gp_state value to a character string. @@ -529,19 +518,30 @@ void show_rcu_gp_kthreads(void) { int cpu; unsigned long j; + unsigned long ja; + unsigned long jr; + unsigned long jw; struct rcu_data *rdp; struct rcu_node *rnp; - j = jiffies - READ_ONCE(rcu_state.gp_activity); - pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %ld\n", + j = jiffies; + ja = j - READ_ONCE(rcu_state.gp_activity); + jr = j - READ_ONCE(rcu_state.gp_req_activity); + jw = j - READ_ONCE(rcu_state.gp_wake_time); + pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", rcu_state.name, gp_state_getname(rcu_state.gp_state), - rcu_state.gp_state, rcu_state.gp_kthread->state, j); + rcu_state.gp_state, + rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL, + ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), + (long)READ_ONCE(rcu_state.gp_seq), + (long)READ_ONCE(rcu_get_root()->gp_seq_needed), + READ_ONCE(rcu_state.gp_flags)); rcu_for_each_node_breadth_first(rnp) { if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed)) continue; - pr_info("\trcu_node %d:%d ->gp_seq %lu ->gp_seq_needed %lu\n", - rnp->grplo, rnp->grphi, rnp->gp_seq, - rnp->gp_seq_needed); + pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n", + rnp->grplo, rnp->grphi, (long)rnp->gp_seq, + (long)rnp->gp_seq_needed); if (!rcu_is_leaf_node(rnp)) continue; for_each_leaf_node_possible_cpu(rnp, cpu) { @@ -550,14 +550,35 @@ void show_rcu_gp_kthreads(void) ULONG_CMP_GE(rcu_state.gp_seq, rdp->gp_seq_needed)) continue; - pr_info("\tcpu %d ->gp_seq_needed %lu\n", - cpu, rdp->gp_seq_needed); + pr_info("\tcpu %d ->gp_seq_needed %ld\n", + cpu, (long)rdp->gp_seq_needed); } } /* sched_show_task(rcu_state.gp_kthread); */ } EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); +/* Dump grace-period-request information due to commandeered sysrq. */ +static void sysrq_show_rcu(int key) +{ + show_rcu_gp_kthreads(); +} + +static struct sysrq_key_op sysrq_rcudump_op = { + .handler = sysrq_show_rcu, + .help_msg = "show-rcu(y)", + .action_msg = "Show RCU tree", + .enable_mask = SYSRQ_ENABLE_DUMP, +}; + +static int __init rcu_sysrq_init(void) +{ + if (sysrq_rcu) + return register_sysrq_key('y', &sysrq_rcudump_op); + return 0; +} +early_initcall(rcu_sysrq_init); + /* * Send along grace-period-related data for rcutorture diagnostics. */ @@ -566,8 +587,6 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, { switch (test_type) { case RCU_FLAVOR: - case RCU_BH_FLAVOR: - case RCU_SCHED_FLAVOR: *flags = READ_ONCE(rcu_state.gp_flags); *gp_seq = rcu_seq_current(&rcu_state.gp_seq); break; @@ -578,14 +597,6 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); /* - * Return the root node of the rcu_state structure. - */ -static struct rcu_node *rcu_get_root(void) -{ - return &rcu_state.node[0]; -} - -/* * Enter an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * @@ -701,7 +712,6 @@ static __always_inline void rcu_nmi_exit_common(bool irq) /** * rcu_nmi_exit - inform RCU of exit from NMI context - * @irq: Is this call from rcu_irq_exit? * * If you add or remove a call to rcu_nmi_exit(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. @@ -1115,7 +1125,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) } /* - * NO_HZ_FULL CPUs can run in-kernel without rcu_check_callbacks! + * NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq! * The above code handles this, but only for straight cond_resched(). * And some in-kernel loops check need_resched() before calling * cond_resched(), which defeats the above code for CPUs that are @@ -1181,7 +1191,7 @@ static void rcu_check_gp_kthread_starvation(void) pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), - rcu_state.gp_flags, + READ_ONCE(rcu_state.gp_flags), gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); if (gpk) { @@ -1310,7 +1320,7 @@ static void print_other_cpu_stall(unsigned long gp_seq) panic_on_rcu_stall(); - force_quiescent_state(); /* Kick them all. */ + rcu_force_quiescent_state(); /* Kick them all. */ } static void print_cpu_stall(void) @@ -1557,17 +1567,28 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) } /* - * Awaken the grace-period kthread. Don't do a self-awaken, and don't - * bother awakening when there is nothing for the grace-period kthread - * to do (as in several CPUs raced to awaken, and we lost), and finally - * don't try to awaken a kthread that has not yet been created. + * Awaken the grace-period kthread. Don't do a self-awaken (unless in + * an interrupt or softirq handler), and don't bother awakening when there + * is nothing for the grace-period kthread to do (as in several CPUs raced + * to awaken, and we lost), and finally don't try to awaken a kthread that + * has not yet been created. If all those checks are passed, track some + * debug information and awaken. + * + * So why do the self-wakeup when in an interrupt or softirq handler + * in the grace-period kthread's context? Because the kthread might have + * been interrupted just as it was going to sleep, and just after the final + * pre-sleep check of the awaken condition. In this case, a wakeup really + * is required, and is therefore supplied. */ static void rcu_gp_kthread_wake(void) { - if (current == rcu_state.gp_kthread || + if ((current == rcu_state.gp_kthread && + !in_interrupt() && !in_serving_softirq()) || !READ_ONCE(rcu_state.gp_flags) || !rcu_state.gp_kthread) return; + WRITE_ONCE(rcu_state.gp_wake_time, jiffies); + WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq)); swake_up_one(&rcu_state.gp_wq); } @@ -1711,7 +1732,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) zero_cpu_stall_ticks(rdp); } rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ - if (ULONG_CMP_GE(rnp->gp_seq_needed, rdp->gp_seq_needed) || rdp->gpwrap) + if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) rdp->gp_seq_needed = rnp->gp_seq_needed; WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); @@ -1939,7 +1960,7 @@ static void rcu_gp_fqs_loop(void) if (!ret) { rcu_state.jiffies_force_qs = jiffies + j; WRITE_ONCE(rcu_state.jiffies_kick_kthreads, - jiffies + 3 * j); + jiffies + (j ? 3 * j : 2)); } trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), @@ -2497,14 +2518,14 @@ static void rcu_do_batch(struct rcu_data *rdp) } /* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. + * This function is invoked from each scheduling-clock interrupt, + * and checks to see if this CPU is in a non-context-switch quiescent + * state, for example, user mode or idle loop. It also schedules RCU + * core processing. If the current grace period has gone on too long, + * it will ask the scheduler to manufacture a context switch for the sole + * purpose of providing a providing the needed quiescent state. */ -void rcu_check_callbacks(int user) +void rcu_sched_clock_irq(int user) { trace_rcu_utilization(TPS("Start scheduler-tick")); raw_cpu_inc(rcu_data.ticks_this_gp); @@ -2517,7 +2538,7 @@ void rcu_check_callbacks(int user) } __this_cpu_write(rcu_data.rcu_urgent_qs, false); } - rcu_flavor_check_callbacks(user); + rcu_flavor_sched_clock_irq(user); if (rcu_pending()) invoke_rcu_core(); @@ -2578,7 +2599,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) * Force quiescent states on reluctant CPUs, and also detect which * CPUs are in dyntick-idle mode. */ -static void force_quiescent_state(void) +void rcu_force_quiescent_state(void) { unsigned long flags; bool ret; @@ -2610,6 +2631,7 @@ static void force_quiescent_state(void) raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* * This function checks for grace-period requests that fail to motivate @@ -2657,16 +2679,11 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } - pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n", - __func__, (long)READ_ONCE(rcu_state.gp_seq), - (long)READ_ONCE(rnp_root->gp_seq_needed), - j - rcu_state.gp_req_activity, j - rcu_state.gp_activity, - rcu_state.gp_flags, rcu_state.gp_state, rcu_state.name, - rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL); WARN_ON(1); if (rnp_root != rnp) raw_spin_unlock_rcu_node(rnp_root); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + show_rcu_gp_kthreads(); } /* @@ -2711,12 +2728,8 @@ void rcu_fwd_progress_check(unsigned long j) } EXPORT_SYMBOL_GPL(rcu_fwd_progress_check); -/* - * This does the RCU core processing work for the specified rcu_data - * structures. This may be called only from the CPU to whom the rdp - * belongs. - */ -static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) +/* Perform RCU core processing work for the current CPU. */ +static __latent_entropy void rcu_core(struct softirq_action *unused) { unsigned long flags; struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); @@ -2801,9 +2814,9 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, /* * Force the grace period if too many callbacks or too long waiting. - * Enforce hysteresis, and don't invoke force_quiescent_state() + * Enforce hysteresis, and don't invoke rcu_force_quiescent_state() * if some other CPU has recently done so. Also, don't bother - * invoking force_quiescent_state() if the newly enqueued callback + * invoking rcu_force_quiescent_state() if the newly enqueued callback * is the only one waiting for a grace period to complete. */ if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > @@ -2820,7 +2833,7 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, rdp->blimit = LONG_MAX; if (rcu_state.n_force_qs == rdp->n_force_qs_snap && rcu_segcblist_first_pend_cb(&rdp->cblist) != head) - force_quiescent_state(); + rcu_force_quiescent_state(); rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); } @@ -2889,9 +2902,6 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func, int cpu, bool lazy) rcu_segcblist_init(&rdp->cblist); } rcu_segcblist_enqueue(&rdp->cblist, head, lazy); - if (!lazy) - rcu_idle_count_callbacks_posted(); - if (__is_kfree_rcu_offset((unsigned long)func)) trace_rcu_kfree_callback(rcu_state.name, head, (unsigned long)func, @@ -2961,6 +2971,79 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) } EXPORT_SYMBOL_GPL(kfree_call_rcu); +/* + * During early boot, any blocking grace-period wait automatically + * implies a grace period. Later on, this is never the case for PREEMPT. + * + * Howevr, because a context switch is a grace period for !PREEMPT, any + * blocking grace-period wait automatically implies a grace period if + * there is only one CPU online at any point time during execution of + * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to + * occasionally incorrectly indicate that there are multiple CPUs online + * when there was in fact only one the whole time, as this just adds some + * overhead: RCU still operates correctly. + */ +static int rcu_blocking_is_gp(void) +{ + int ret; + + if (IS_ENABLED(CONFIG_PREEMPT)) + return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE; + might_sleep(); /* Check for RCU read-side critical section. */ + preempt_disable(); + ret = num_online_cpus() <= 1; + preempt_enable(); + return ret; +} + +/** + * synchronize_rcu - wait until a grace period has elapsed. + * + * Control will return to the caller some time after a full grace + * period has elapsed, in other words after all currently executing RCU + * read-side critical sections have completed. Note, however, that + * upon return from synchronize_rcu(), the caller might well be executing + * concurrently with new RCU read-side critical sections that began while + * synchronize_rcu() was waiting. RCU read-side critical sections are + * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. + * In addition, regions of code across which interrupts, preemption, or + * softirqs have been disabled also serve as RCU read-side critical + * sections. This includes hardware interrupt handlers, softirq handlers, + * and NMI handlers. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_rcu() returns, + * each CPU is guaranteed to have executed a full memory barrier since + * the end of its last RCU read-side critical section whose beginning + * preceded the call to synchronize_rcu(). In addition, each CPU having + * an RCU read-side critical section that extends beyond the return from + * synchronize_rcu() is guaranteed to have executed a full memory barrier + * after the beginning of synchronize_rcu() and before the beginning of + * that RCU read-side critical section. Note that these guarantees include + * CPUs that are offline, idle, or executing in user mode, as well as CPUs + * that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_rcu(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + */ +void synchronize_rcu(void) +{ + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu() in RCU read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_expedited(); + else + wait_rcu_gp(call_rcu); +} +EXPORT_SYMBOL_GPL(synchronize_rcu); + /** * get_state_synchronize_rcu - Snapshot current RCU state * @@ -3049,28 +3132,6 @@ static int rcu_pending(void) } /* - * Return true if the specified CPU has any callback. If all_lazy is - * non-NULL, store an indication of whether all callbacks are lazy. - * (If there are no callbacks, all of them are deemed to be lazy.) - */ -static bool rcu_cpu_has_callbacks(bool *all_lazy) -{ - bool al = true; - bool hc = false; - struct rcu_data *rdp; - - rdp = this_cpu_ptr(&rcu_data); - if (!rcu_segcblist_empty(&rdp->cblist)) { - hc = true; - if (rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)) - al = false; - } - if (all_lazy) - *all_lazy = al; - return hc; -} - -/* * Helper function for rcu_barrier() tracing. If tracing is disabled, * the compiler is expected to optimize this away. */ @@ -3299,7 +3360,7 @@ int rcutree_prepare_cpu(unsigned int cpu) trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_prepare_kthreads(cpu); - rcu_spawn_all_nocb_kthreads(cpu); + rcu_spawn_cpu_nocb_kthread(cpu); return 0; } @@ -3329,8 +3390,6 @@ int rcutree_online_cpu(unsigned int cpu) raw_spin_lock_irqsave_rcu_node(rnp, flags); rnp->ffmask |= rdp->grpmask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - if (IS_ENABLED(CONFIG_TREE_SRCU)) - srcu_online_cpu(cpu); if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return 0; /* Too early in boot for scheduler work. */ sync_sched_exp_online_cleanup(cpu); @@ -3355,8 +3414,6 @@ int rcutree_offline_cpu(unsigned int cpu) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcutree_affinity_setting(cpu, cpu); - if (IS_ENABLED(CONFIG_TREE_SRCU)) - srcu_offline_cpu(cpu); return 0; } @@ -3777,7 +3834,7 @@ void __init rcu_init(void) rcu_init_one(); if (dump_tree) rcu_dump_rcu_node_tree(); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + open_softirq(RCU_SOFTIRQ, rcu_core); /* * We don't need protection against CPU-hotplug here because diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index d90b02b53c0e..bb4f995f2d3f 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -1,25 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2008 * * Author: Ingo Molnar <mingo@elte.hu> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Paul E. McKenney <paulmck@linux.ibm.com> */ #include <linux/cache.h> @@ -36,7 +23,6 @@ /* Communicate arguments to a workqueue handler. */ struct rcu_exp_work { - smp_call_func_t rew_func; unsigned long rew_s; struct work_struct rew_work; }; @@ -194,10 +180,7 @@ struct rcu_data { bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ bool rcu_urgent_qs; /* GP old need light quiescent state. */ #ifdef CONFIG_RCU_FAST_NO_HZ - bool all_lazy; /* Are all CPU's CBs lazy? */ - unsigned long nonlazy_posted; /* # times non-lazy CB posted to CPU. */ - unsigned long nonlazy_posted_snap; - /* Nonlazy_posted snapshot. */ + bool all_lazy; /* All CPU's CBs lazy at idle start? */ unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */ unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */ int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ @@ -234,7 +217,13 @@ struct rcu_data { /* Leader CPU takes GP-end wakeups. */ #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ - /* 6) Diagnostic data, including RCU CPU stall warnings. */ + /* 6) RCU priority boosting. */ + struct task_struct *rcu_cpu_kthread_task; + /* rcuc per-CPU kthread or NULL. */ + unsigned int rcu_cpu_kthread_status; + char rcu_cpu_has_work; + + /* 7) Diagnostic data, including RCU CPU stall warnings. */ unsigned int softirq_snap; /* Snapshot of softirq activity. */ /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ struct irq_work rcu_iw; /* Check for non-irq activity. */ @@ -303,6 +292,8 @@ struct rcu_state { struct swait_queue_head gp_wq; /* Where GP task waits. */ short gp_flags; /* Commands for GP task. */ short gp_state; /* GP kthread sleep state. */ + unsigned long gp_wake_time; /* Last GP kthread wake. */ + unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ /* End of fields guarded by root rcu_node's lock. */ @@ -402,13 +393,6 @@ static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; int rcu_dynticks_snap(struct rcu_data *rdp); -#ifdef CONFIG_RCU_BOOST -DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); -DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DECLARE_PER_CPU(char, rcu_cpu_has_work); -#endif /* #ifdef CONFIG_RCU_BOOST */ - /* Forward declarations for rcutree_plugin.h */ static void rcu_bootup_announce(void); static void rcu_qs(void); @@ -420,7 +404,7 @@ static void rcu_print_detail_task_stall(void); static int rcu_print_task_stall(struct rcu_node *rnp); static int rcu_print_task_exp_stall(struct rcu_node *rnp); static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); -static void rcu_flavor_check_callbacks(int user); +static void rcu_flavor_sched_clock_irq(int user); void call_rcu(struct rcu_head *head, rcu_callback_t func); static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); @@ -431,7 +415,6 @@ static void __init rcu_spawn_boost_kthreads(void); static void rcu_prepare_kthreads(int cpu); static void rcu_cleanup_after_idle(void); static void rcu_prepare_for_idle(void); -static void rcu_idle_count_callbacks_posted(void); static bool rcu_preempt_has_tasks(struct rcu_node *rnp); static bool rcu_preempt_need_deferred_qs(struct task_struct *t); static void rcu_preempt_deferred_qs(struct task_struct *t); @@ -451,7 +434,7 @@ static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); static void do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); -static void rcu_spawn_all_nocb_kthreads(int cpu); +static void rcu_spawn_cpu_nocb_kthread(int cpu); static void __init rcu_spawn_nocb_kthreads(void); #ifdef CONFIG_RCU_NOCB_CPU static void __init rcu_organize_nocb_kthreads(void); @@ -462,11 +445,3 @@ static void rcu_bind_gp_kthread(void); static bool rcu_nohz_full_cpu(void); static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); - -#ifdef CONFIG_SRCU -void srcu_online_cpu(unsigned int cpu); -void srcu_offline_cpu(unsigned int cpu); -#else /* #ifdef CONFIG_SRCU */ -void srcu_online_cpu(unsigned int cpu) { } -void srcu_offline_cpu(unsigned int cpu) { } -#endif /* #else #ifdef CONFIG_SRCU */ diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 928fe5893a57..4c2a0189e748 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -1,27 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * RCU expedited grace periods * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2016 * - * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Authors: Paul E. McKenney <paulmck@linux.ibm.com> */ #include <linux/lockdep.h> +static void rcu_exp_handler(void *unused); + /* * Record the start of an expedited grace period. */ @@ -344,7 +333,6 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) { int cpu; unsigned long flags; - smp_call_func_t func; unsigned long mask_ofl_test; unsigned long mask_ofl_ipi; int ret; @@ -352,7 +340,6 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) container_of(wp, struct rcu_exp_work, rew_work); struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); - func = rewp->rew_func; raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Each pass checks a CPU for identity, offline, and idle. */ @@ -396,7 +383,7 @@ retry_ipi: mask_ofl_test |= mask; continue; } - ret = smp_call_function_single(cpu, func, NULL, 0); + ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); if (!ret) { mask_ofl_ipi &= ~mask; continue; @@ -426,7 +413,7 @@ retry_ipi: * Select the nodes that the upcoming expedited grace period needs * to wait for. */ -static void sync_rcu_exp_select_cpus(smp_call_func_t func) +static void sync_rcu_exp_select_cpus(void) { int cpu; struct rcu_node *rnp; @@ -440,7 +427,6 @@ static void sync_rcu_exp_select_cpus(smp_call_func_t func) rnp->exp_need_flush = false; if (!READ_ONCE(rnp->expmask)) continue; /* Avoid early boot non-existent wq. */ - rnp->rew.rew_func = func; if (!READ_ONCE(rcu_par_gp_wq) || rcu_scheduler_active != RCU_SCHEDULER_RUNNING || rcu_is_last_leaf_node(rnp)) { @@ -449,7 +435,6 @@ static void sync_rcu_exp_select_cpus(smp_call_func_t func) continue; } INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); - preempt_disable(); cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1); /* If all offline, queue the work on an unbound CPU. */ if (unlikely(cpu > rnp->grphi - rnp->grplo)) @@ -457,7 +442,6 @@ static void sync_rcu_exp_select_cpus(smp_call_func_t func) else cpu += rnp->grplo; queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work); - preempt_enable(); rnp->exp_need_flush = true; } @@ -580,10 +564,10 @@ static void rcu_exp_wait_wake(unsigned long s) * Common code to drive an expedited grace period forward, used by * workqueues and mid-boot-time tasks. */ -static void rcu_exp_sel_wait_wake(smp_call_func_t func, unsigned long s) +static void rcu_exp_sel_wait_wake(unsigned long s) { /* Initialize the rcu_node tree in preparation for the wait. */ - sync_rcu_exp_select_cpus(func); + sync_rcu_exp_select_cpus(); /* Wait and clean up, including waking everyone. */ rcu_exp_wait_wake(s); @@ -597,52 +581,7 @@ static void wait_rcu_exp_gp(struct work_struct *wp) struct rcu_exp_work *rewp; rewp = container_of(wp, struct rcu_exp_work, rew_work); - rcu_exp_sel_wait_wake(rewp->rew_func, rewp->rew_s); -} - -/* - * Given a smp_call_function() handler, kick off the specified - * implementation of expedited grace period. - */ -static void _synchronize_rcu_expedited(smp_call_func_t func) -{ - struct rcu_data *rdp; - struct rcu_exp_work rew; - struct rcu_node *rnp; - unsigned long s; - - /* If expedited grace periods are prohibited, fall back to normal. */ - if (rcu_gp_is_normal()) { - wait_rcu_gp(call_rcu); - return; - } - - /* Take a snapshot of the sequence number. */ - s = rcu_exp_gp_seq_snap(); - if (exp_funnel_lock(s)) - return; /* Someone else did our work for us. */ - - /* Ensure that load happens before action based on it. */ - if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { - /* Direct call during scheduler init and early_initcalls(). */ - rcu_exp_sel_wait_wake(func, s); - } else { - /* Marshall arguments & schedule the expedited grace period. */ - rew.rew_func = func; - rew.rew_s = s; - INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); - queue_work(rcu_gp_wq, &rew.rew_work); - } - - /* Wait for expedited grace period to complete. */ - rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); - rnp = rcu_get_root(); - wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], - sync_exp_work_done(s)); - smp_mb(); /* Workqueue actions happen before return. */ - - /* Let the next expedited grace period start. */ - mutex_unlock(&rcu_state.exp_mutex); + rcu_exp_sel_wait_wake(rewp->rew_s); } #ifdef CONFIG_PREEMPT_RCU @@ -654,7 +593,7 @@ static void _synchronize_rcu_expedited(smp_call_func_t func) * ->expmask fields in the rcu_node tree. Otherwise, immediately * report the quiescent state. */ -static void sync_rcu_exp_handler(void *unused) +static void rcu_exp_handler(void *unused) { unsigned long flags; struct rcu_data *rdp = this_cpu_ptr(&rcu_data); @@ -697,6 +636,7 @@ static void sync_rcu_exp_handler(void *unused) WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true); } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; } /* @@ -730,43 +670,10 @@ static void sync_sched_exp_online_cleanup(int cpu) { } -/** - * synchronize_rcu_expedited - Brute-force RCU grace period - * - * Wait for an RCU-preempt grace period, but expedite it. The basic - * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler - * checks whether the CPU is in an RCU-preempt critical section, and - * if so, it sets a flag that causes the outermost rcu_read_unlock() - * to report the quiescent state. On the other hand, if the CPU is - * not in an RCU read-side critical section, the IPI handler reports - * the quiescent state immediately. - * - * Although this is a greate improvement over previous expedited - * implementations, it is still unfriendly to real-time workloads, so is - * thus not recommended for any sort of common-case code. In fact, if - * you are using synchronize_rcu_expedited() in a loop, please restructure - * your code to batch your updates, and then Use a single synchronize_rcu() - * instead. - * - * This has the same semantics as (but is more brutal than) synchronize_rcu(). - */ -void synchronize_rcu_expedited(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); - - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) - return; - _synchronize_rcu_expedited(sync_rcu_exp_handler); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - #else /* #ifdef CONFIG_PREEMPT_RCU */ /* Invoked on each online non-idle CPU for expedited quiescent state. */ -static void sync_sched_exp_handler(void *unused) +static void rcu_exp_handler(void *unused) { struct rcu_data *rdp; struct rcu_node *rnp; @@ -798,44 +705,78 @@ static void sync_sched_exp_online_cleanup(int cpu) rnp = rdp->mynode; if (!(READ_ONCE(rnp->expmask) & rdp->grpmask)) return; - ret = smp_call_function_single(cpu, sync_sched_exp_handler, NULL, 0); + ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0); WARN_ON_ONCE(ret); } -/* - * Because a context switch is a grace period for !PREEMPT, any - * blocking grace-period wait automatically implies a grace period if - * there is only one CPU online at any point time during execution of - * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to - * occasionally incorrectly indicate that there are multiple CPUs online - * when there was in fact only one the whole time, as this just adds some - * overhead: RCU still operates correctly. - */ -static int rcu_blocking_is_gp(void) -{ - int ret; - - might_sleep(); /* Check for RCU read-side critical section. */ - preempt_disable(); - ret = num_online_cpus() <= 1; - preempt_enable(); - return ret; -} +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ -/* PREEMPT=n implementation of synchronize_rcu_expedited(). */ +/** + * synchronize_rcu_expedited - Brute-force RCU grace period + * + * Wait for an RCU grace period, but expedite it. The basic idea is to + * IPI all non-idle non-nohz online CPUs. The IPI handler checks whether + * the CPU is in an RCU critical section, and if so, it sets a flag that + * causes the outermost rcu_read_unlock() to report the quiescent state + * for RCU-preempt or asks the scheduler for help for RCU-sched. On the + * other hand, if the CPU is not in an RCU read-side critical section, + * the IPI handler reports the quiescent state immediately. + * + * Although this is a greate improvement over previous expedited + * implementations, it is still unfriendly to real-time workloads, so is + * thus not recommended for any sort of common-case code. In fact, if + * you are using synchronize_rcu_expedited() in a loop, please restructure + * your code to batch your updates, and then Use a single synchronize_rcu() + * instead. + * + * This has the same semantics as (but is more brutal than) synchronize_rcu(). + */ void synchronize_rcu_expedited(void) { + struct rcu_data *rdp; + struct rcu_exp_work rew; + struct rcu_node *rnp; + unsigned long s; + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map), "Illegal synchronize_rcu_expedited() in RCU read-side critical section"); - /* If only one CPU, this is automatically a grace period. */ + /* Is the state is such that the call is a grace period? */ if (rcu_blocking_is_gp()) return; - _synchronize_rcu_expedited(sync_sched_exp_handler); + /* If expedited grace periods are prohibited, fall back to normal. */ + if (rcu_gp_is_normal()) { + wait_rcu_gp(call_rcu); + return; + } + + /* Take a snapshot of the sequence number. */ + s = rcu_exp_gp_seq_snap(); + if (exp_funnel_lock(s)) + return; /* Someone else did our work for us. */ + + /* Ensure that load happens before action based on it. */ + if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) { + /* Direct call during scheduler init and early_initcalls(). */ + rcu_exp_sel_wait_wake(s); + } else { + /* Marshall arguments & schedule the expedited grace period. */ + rew.rew_s = s; + INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); + queue_work(rcu_gp_wq, &rew.rew_work); + } + + /* Wait for expedited grace period to complete. */ + rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id()); + rnp = rcu_get_root(); + wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], + sync_exp_work_done(s)); + smp_mb(); /* Workqueue actions happen before return. */ + + /* Let the next expedited grace period start. */ + mutex_unlock(&rcu_state.exp_mutex); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); - -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 1b3dd2fc0cd6..97dba50f6fb2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1,27 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions that provide either classic * or preemptible semantics. * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright Red Hat, 2009 * Copyright IBM Corporation, 2009 * * Author: Ingo Molnar <mingo@elte.hu> - * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * Paul E. McKenney <paulmck@linux.ibm.com> */ #include <linux/delay.h> @@ -34,17 +21,7 @@ #include "../time/tick-internal.h" #ifdef CONFIG_RCU_BOOST - #include "../locking/rtmutex_common.h" - -/* - * Control variables for per-CPU and per-rcu_node kthreads. - */ -static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); -DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); -DEFINE_PER_CPU(char, rcu_cpu_has_work); - #else /* #ifdef CONFIG_RCU_BOOST */ /* @@ -307,7 +284,7 @@ static void rcu_qs(void) __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); - barrier(); /* Coordinate with rcu_flavor_check_callbacks(). */ + barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ current->rcu_read_unlock_special.b.need_qs = false; } } @@ -788,13 +765,13 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) } /* - * Check for a quiescent state from the current CPU. When a task blocks, - * the task is recorded in the corresponding CPU's rcu_node structure, - * which is checked elsewhere. - * - * Caller must disable hard irqs. + * Check for a quiescent state from the current CPU, including voluntary + * context switches for Tasks RCU. When a task blocks, the task is + * recorded in the corresponding CPU's rcu_node structure, which is checked + * elsewhere, hence this function need only check for quiescent states + * related to the current CPU, not to those related to tasks. */ -static void rcu_flavor_check_callbacks(int user) +static void rcu_flavor_sched_clock_irq(int user) { struct task_struct *t = current; @@ -825,54 +802,6 @@ static void rcu_flavor_check_callbacks(int user) t->rcu_read_unlock_special.b.need_qs = true; } -/** - * synchronize_rcu - wait until a grace period has elapsed. - * - * Control will return to the caller some time after a full grace - * period has elapsed, in other words after all currently executing RCU - * read-side critical sections have completed. Note, however, that - * upon return from synchronize_rcu(), the caller might well be executing - * concurrently with new RCU read-side critical sections that began while - * synchronize_rcu() was waiting. RCU read-side critical sections are - * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. - * In addition, regions of code across which interrupts, preemption, or - * softirqs have been disabled also serve as RCU read-side critical - * sections. This includes hardware interrupt handlers, softirq handlers, - * and NMI handlers. - * - * Note that this guarantee implies further memory-ordering guarantees. - * On systems with more than one CPU, when synchronize_rcu() returns, - * each CPU is guaranteed to have executed a full memory barrier since - * the end of its last RCU read-side critical section whose beginning - * preceded the call to synchronize_rcu(). In addition, each CPU having - * an RCU read-side critical section that extends beyond the return from - * synchronize_rcu() is guaranteed to have executed a full memory barrier - * after the beginning of synchronize_rcu() and before the beginning of - * that RCU read-side critical section. Note that these guarantees include - * CPUs that are offline, idle, or executing in user mode, as well as CPUs - * that are executing in the kernel. - * - * Furthermore, if CPU A invoked synchronize_rcu(), which returned - * to its caller on CPU B, then both CPU A and CPU B are guaranteed - * to have executed a full memory barrier during the execution of - * synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but - * again only if the system has more than one CPU). - */ -void synchronize_rcu(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu() in RCU read-side critical section"); - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) - return; - if (rcu_gp_is_expedited()) - synchronize_rcu_expedited(); - else - wait_rcu_gp(call_rcu); -} -EXPORT_SYMBOL_GPL(synchronize_rcu); - /* * Check for a task exiting while in a preemptible-RCU read-side * critical section, clean up if so. No need to issue warnings, @@ -1088,14 +1017,10 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) } /* - * Check to see if this CPU is in a non-context-switch quiescent state - * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). - * Also schedule RCU core processing. - * - * This function must be called from hardirq context. It is normally - * invoked from the scheduling-clock interrupt. + * Check to see if this CPU is in a non-context-switch quiescent state, + * namely user mode and idle loop. */ -static void rcu_flavor_check_callbacks(int user) +static void rcu_flavor_sched_clock_irq(int user) { if (user || rcu_is_cpu_rrupt_from_idle()) { @@ -1115,22 +1040,6 @@ static void rcu_flavor_check_callbacks(int user) } } -/* PREEMPT=n implementation of synchronize_rcu(). */ -void synchronize_rcu(void) -{ - RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_rcu() in RCU read-side critical section"); - if (rcu_blocking_is_gp()) - return; - if (rcu_gp_is_expedited()) - synchronize_rcu_expedited(); - else - wait_rcu_gp(call_rcu); -} -EXPORT_SYMBOL_GPL(synchronize_rcu); - /* * Because preemptible RCU does not exist, tasks cannot possibly exit * while in preemptible RCU read-side critical sections. @@ -1307,11 +1216,11 @@ static void invoke_rcu_callbacks_kthread(void) unsigned long flags; local_irq_save(flags); - __this_cpu_write(rcu_cpu_has_work, 1); - if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && - current != __this_cpu_read(rcu_cpu_kthread_task)) { - rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), - __this_cpu_read(rcu_cpu_kthread_status)); + __this_cpu_write(rcu_data.rcu_cpu_has_work, 1); + if (__this_cpu_read(rcu_data.rcu_cpu_kthread_task) != NULL && + current != __this_cpu_read(rcu_data.rcu_cpu_kthread_task)) { + rcu_wake_cond(__this_cpu_read(rcu_data.rcu_cpu_kthread_task), + __this_cpu_read(rcu_data.rcu_cpu_kthread_status)); } local_irq_restore(flags); } @@ -1322,7 +1231,7 @@ static void invoke_rcu_callbacks_kthread(void) */ static bool rcu_is_callbacks_kthread(void) { - return __this_cpu_read(rcu_cpu_kthread_task) == current; + return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current; } #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) @@ -1369,11 +1278,6 @@ static int rcu_spawn_one_boost_kthread(struct rcu_node *rnp) return 0; } -static void rcu_kthread_do_work(void) -{ - rcu_do_batch(this_cpu_ptr(&rcu_data)); -} - static void rcu_cpu_kthread_setup(unsigned int cpu) { struct sched_param sp; @@ -1384,12 +1288,12 @@ static void rcu_cpu_kthread_setup(unsigned int cpu) static void rcu_cpu_kthread_park(unsigned int cpu) { - per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; + per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; } static int rcu_cpu_kthread_should_run(unsigned int cpu) { - return __this_cpu_read(rcu_cpu_has_work); + return __this_cpu_read(rcu_data.rcu_cpu_has_work); } /* @@ -1399,21 +1303,20 @@ static int rcu_cpu_kthread_should_run(unsigned int cpu) */ static void rcu_cpu_kthread(unsigned int cpu) { - unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); - char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); + unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status); + char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work); int spincnt; for (spincnt = 0; spincnt < 10; spincnt++) { trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); local_bh_disable(); *statusp = RCU_KTHREAD_RUNNING; - this_cpu_inc(rcu_cpu_kthread_loops); local_irq_disable(); work = *workp; *workp = 0; local_irq_enable(); if (work) - rcu_kthread_do_work(); + rcu_do_batch(this_cpu_ptr(&rcu_data)); local_bh_enable(); if (*workp == 0) { trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); @@ -1459,7 +1362,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) } static struct smp_hotplug_thread rcu_cpu_thread_spec = { - .store = &rcu_cpu_kthread_task, + .store = &rcu_data.rcu_cpu_kthread_task, .thread_should_run = rcu_cpu_kthread_should_run, .thread_fn = rcu_cpu_kthread, .thread_comm = "rcuc/%u", @@ -1476,7 +1379,7 @@ static void __init rcu_spawn_boost_kthreads(void) int cpu; for_each_possible_cpu(cpu) - per_cpu(rcu_cpu_has_work, cpu) = 0; + per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0; if (WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcub kthread, OOM is now expected behavior\n", __func__)) return; rcu_for_each_leaf_node(rnp) @@ -1543,7 +1446,7 @@ static void rcu_prepare_kthreads(int cpu) int rcu_needs_cpu(u64 basemono, u64 *nextevt) { *nextevt = KTIME_MAX; - return rcu_cpu_has_callbacks(NULL); + return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist); } /* @@ -1562,14 +1465,6 @@ static void rcu_prepare_for_idle(void) { } -/* - * Don't bother keeping a running count of the number of RCU callbacks - * posted because CONFIG_RCU_FAST_NO_HZ=n. - */ -static void rcu_idle_count_callbacks_posted(void) -{ -} - #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ /* @@ -1652,11 +1547,8 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) lockdep_assert_irqs_disabled(); - /* Snapshot to detect later posting of non-lazy callback. */ - rdp->nonlazy_posted_snap = rdp->nonlazy_posted; - /* If no callbacks, RCU doesn't need the CPU. */ - if (!rcu_cpu_has_callbacks(&rdp->all_lazy)) { + if (rcu_segcblist_empty(&rdp->cblist)) { *nextevt = KTIME_MAX; return 0; } @@ -1670,11 +1562,12 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) rdp->last_accelerate = jiffies; /* Request timer delay depending on laziness, and round. */ - if (!rdp->all_lazy) { + rdp->all_lazy = !rcu_segcblist_n_nonlazy_cbs(&rdp->cblist); + if (rdp->all_lazy) { + dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; + } else { dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies; - } else { - dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; } *nextevt = basemono + dj * TICK_NSEC; return 0; @@ -1704,7 +1597,7 @@ static void rcu_prepare_for_idle(void) /* Handle nohz enablement switches conservatively. */ tne = READ_ONCE(tick_nohz_active); if (tne != rdp->tick_nohz_enabled_snap) { - if (rcu_cpu_has_callbacks(NULL)) + if (!rcu_segcblist_empty(&rdp->cblist)) invoke_rcu_core(); /* force nohz to see update. */ rdp->tick_nohz_enabled_snap = tne; return; @@ -1717,10 +1610,8 @@ static void rcu_prepare_for_idle(void) * callbacks, invoke RCU core for the side-effect of recalculating * idle duration on re-entry to idle. */ - if (rdp->all_lazy && - rdp->nonlazy_posted != rdp->nonlazy_posted_snap) { + if (rdp->all_lazy && rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)) { rdp->all_lazy = false; - rdp->nonlazy_posted_snap = rdp->nonlazy_posted; invoke_rcu_core(); return; } @@ -1756,19 +1647,6 @@ static void rcu_cleanup_after_idle(void) invoke_rcu_core(); } -/* - * Keep a running count of the number of non-lazy callbacks posted - * on this CPU. This running counter (which is never decremented) allows - * rcu_prepare_for_idle() to detect when something out of the idle loop - * posts a callback, even if an equal number of callbacks are invoked. - * Of course, callbacks should only be posted from within a trace event - * designed to be called from idle or from within RCU_NONIDLE(). - */ -static void rcu_idle_count_callbacks_posted(void) -{ - __this_cpu_add(rcu_data.nonlazy_posted, 1); -} - #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #ifdef CONFIG_RCU_FAST_NO_HZ @@ -1776,13 +1654,12 @@ static void rcu_idle_count_callbacks_posted(void) static void print_cpu_stall_fast_no_hz(char *cp, int cpu) { struct rcu_data *rdp = &per_cpu(rcu_data, cpu); - unsigned long nlpd = rdp->nonlazy_posted - rdp->nonlazy_posted_snap; - sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", + sprintf(cp, "last_accelerate: %04lx/%04lx, Nonlazy posted: %c%c%c", rdp->last_accelerate & 0xffff, jiffies & 0xffff, - ulong2long(nlpd), - rdp->all_lazy ? 'L' : '.', - rdp->tick_nohz_enabled_snap ? '.' : 'D'); + ".l"[rdp->all_lazy], + ".L"[!rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)], + ".D"[!rdp->tick_nohz_enabled_snap]); } #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ @@ -1868,22 +1745,24 @@ static void zero_cpu_stall_ticks(struct rcu_data *rdp) /* * Offload callback processing from the boot-time-specified set of CPUs - * specified by rcu_nocb_mask. For each CPU in the set, there is a - * kthread created that pulls the callbacks from the corresponding CPU, - * waits for a grace period to elapse, and invokes the callbacks. - * The no-CBs CPUs do a wake_up() on their kthread when they insert - * a callback into any empty list, unless the rcu_nocb_poll boot parameter - * has been specified, in which case each kthread actively polls its - * CPU. (Which isn't so great for energy efficiency, but which does - * reduce RCU's overhead on that CPU.) + * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads + * created that pull the callbacks from the corresponding CPU, wait for + * a grace period to elapse, and invoke the callbacks. These kthreads + * are organized into leaders, which manage incoming callbacks, wait for + * grace periods, and awaken followers, and the followers, which only + * invoke callbacks. Each leader is its own follower. The no-CBs CPUs + * do a wake_up() on their kthread when they insert a callback into any + * empty list, unless the rcu_nocb_poll boot parameter has been specified, + * in which case each kthread actively polls its CPU. (Which isn't so great + * for energy efficiency, but which does reduce RCU's overhead on that CPU.) * * This is intended to be used in conjunction with Frederic Weisbecker's * adaptive-idle work, which would seriously reduce OS jitter on CPUs * running CPU-bound user-mode computations. * - * Offloading of callback processing could also in theory be used as - * an energy-efficiency measure because CPUs with no RCU callbacks - * queued are more aggressive about entering dyntick-idle mode. + * Offloading of callbacks can also be used as an energy-efficiency + * measure because CPUs with no RCU callbacks queued are more aggressive + * about entering dyntick-idle mode. */ @@ -1987,10 +1866,7 @@ static void wake_nocb_leader_defer(struct rcu_data *rdp, int waketype, raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); } -/* - * Does the specified CPU need an RCU callback for this invocation - * of rcu_barrier()? - */ +/* Does rcu_barrier need to queue an RCU callback on the specified CPU? */ static bool rcu_nocb_cpu_needs_barrier(int cpu) { struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); @@ -2006,8 +1882,8 @@ static bool rcu_nocb_cpu_needs_barrier(int cpu) * callbacks would be posted. In the worst case, the first * barrier in rcu_barrier() suffices (but the caller cannot * necessarily rely on this, not a substitute for the caller - * getting the concurrency design right!). There must also be - * a barrier between the following load an posting of a callback + * getting the concurrency design right!). There must also be a + * barrier between the following load and posting of a callback * (if a callback is in fact needed). This is associated with an * atomic_inc() in the caller. */ @@ -2517,9 +2393,9 @@ static void rcu_spawn_one_nocb_kthread(int cpu) /* * If the specified CPU is a no-CBs CPU that does not already have its - * rcuo kthreads, spawn them. + * rcuo kthread, spawn it. */ -static void rcu_spawn_all_nocb_kthreads(int cpu) +static void rcu_spawn_cpu_nocb_kthread(int cpu) { if (rcu_scheduler_fully_active) rcu_spawn_one_nocb_kthread(cpu); @@ -2536,7 +2412,7 @@ static void __init rcu_spawn_nocb_kthreads(void) int cpu; for_each_online_cpu(cpu) - rcu_spawn_all_nocb_kthreads(cpu); + rcu_spawn_cpu_nocb_kthread(cpu); } /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ @@ -2670,7 +2546,7 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) { } -static void rcu_spawn_all_nocb_kthreads(int cpu) +static void rcu_spawn_cpu_nocb_kthread(int cpu) { } diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 1971869c4072..e3c6395c9b4c 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -1,26 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0+ /* * Read-Copy Update mechanism for mutual exclusion * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * * Copyright IBM Corporation, 2001 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> * Manfred Spraul <manfred@colorfullife.com> * - * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * Based on the original work by Paul McKenney <paulmck@linux.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |