diff options
| -rw-r--r-- | include/linux/rcupdate.h | 4 | ||||
| -rw-r--r-- | kernel/rcu/rcu.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/tiny_plugin.h | 9 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 33 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 52 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 38 |
7 files changed, 104 insertions, 35 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 321f9ed552a9..01f71e1d2e94 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -444,6 +444,10 @@ bool __rcu_is_watching(void); #error "Unknown RCU implementation specified to kernel configuration" #endif +#define RCU_SCHEDULER_INACTIVE 0 +#define RCU_SCHEDULER_INIT 1 +#define RCU_SCHEDULER_RUNNING 2 + /* * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic * initialization and destruction of rcu_head on the stack. rcu_head structures diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 80adef7d4c3d..0d6ff3e471be 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -136,6 +136,7 @@ int rcu_jiffies_till_stall_check(void); #define TPS(x) tracepoint_string(x) void rcu_early_boot_tests(void); +void rcu_test_sync_prims(void); /* * This function really isn't for public consumption, but RCU is special in diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h index 196f0302e2f4..c64b827ecbca 100644 --- a/kernel/rcu/tiny_plugin.h +++ b/kernel/rcu/tiny_plugin.h @@ -60,12 +60,17 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active); /* * During boot, we forgive RCU lockdep issues. After this function is - * invoked, we start taking RCU lockdep issues seriously. + * invoked, we start taking RCU lockdep issues seriously. Note that unlike + * Tree RCU, Tiny RCU transitions directly from RCU_SCHEDULER_INACTIVE + * to RCU_SCHEDULER_RUNNING, skipping the RCU_SCHEDULER_INIT stage. + * The reason for this is that Tiny RCU does not need kthreads, so does + * not have to care about the fact that the scheduler is half-initialized + * at a certain phase of the boot process. */ void __init rcu_scheduler_starting(void) { WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; + rcu_scheduler_active = RCU_SCHEDULER_RUNNING; } #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 96c52e43f7ca..cb4e2056ccf3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -127,13 +127,16 @@ int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ int sysctl_panic_on_rcu_stall __read_mostly; /* - * The rcu_scheduler_active variable transitions from zero to one just - * before the first task is spawned. So when this variable is zero, RCU - * can assume that there is but one task, allowing RCU to (for example) + * The rcu_scheduler_active variable is initialized to the value + * RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the + * first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE, + * RCU can assume that there is but one task, allowing RCU to (for example) * optimize synchronize_rcu() to a simple barrier(). When this variable - * is one, RCU must actually do all the hard work required to detect real - * grace periods. This variable is also used to suppress boot-time false - * positives from lockdep-RCU error checking. + * is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required + * to detect real grace periods. This variable is also used to suppress + * boot-time false positives from lockdep-RCU error checking. Finally, it + * transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU + * is fully initialized, including all of its kthreads having been spawned. */ int rcu_scheduler_active __read_mostly; EXPORT_SYMBOL_GPL(rcu_scheduler_active); @@ -3980,18 +3983,22 @@ static int __init rcu_spawn_gp_kthread(void) early_initcall(rcu_spawn_gp_kthread); /* - * This function is invoked towards the end of the scheduler's initialization - * process. Before this is called, the idle task might contain - * RCU read-side critical sections (during which time, this idle - * task is booting the system). After this function is called, the - * idle tasks are prohibited from containing RCU read-side critical - * sections. This function also enables RCU lockdep checking. + * This function is invoked towards the end of the scheduler's + * initialization process. Before this is called, the idle task might + * contain synchronous grace-period primitives (during which time, this idle + * task is booting the system, and such primitives are no-ops). After this + * function is called, any synchronous grace-period primitives are run as + * expedited, with the requesting task driving the grace period forward. + * A later core_initcall() rcu_exp_runtime_mode() will switch to full + * runtime RCU functionality. */ void rcu_scheduler_starting(void) { WARN_ON(num_online_cpus() != 1); WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; + rcu_test_sync_prims(); + rcu_scheduler_active = RCU_SCHEDULER_INIT; + rcu_test_sync_prims(); } /* diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index d3053e99fdb6..e59e1849b89a 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -532,18 +532,28 @@ struct rcu_exp_work { }; /* + * Common code to drive an expedited grace period forward, used by + * workqueues and mid-boot-time tasks. + */ +static void rcu_exp_sel_wait_wake(struct rcu_state *rsp, + smp_call_func_t func, unsigned long s) +{ + /* Initialize the rcu_node tree in preparation for the wait. */ + sync_rcu_exp_select_cpus(rsp, func); + + /* Wait and clean up, including waking everyone. */ + rcu_exp_wait_wake(rsp, s); +} + +/* * Work-queue handler to drive an expedited grace period forward. */ static void wait_rcu_exp_gp(struct work_struct *wp) { struct rcu_exp_work *rewp; - /* Initialize the rcu_node tree in preparation for the wait. */ rewp = container_of(wp, struct rcu_exp_work, rew_work); - sync_rcu_exp_select_cpus(rewp->rew_rsp, rewp->rew_func); - - /* Wait and clean up, including waking everyone. */ - rcu_exp_wait_wake(rewp->rew_rsp, rewp->rew_s); + rcu_exp_sel_wait_wake(rewp->rew_rsp, rewp->rew_func, rewp->rew_s); } /* @@ -569,12 +579,18 @@ static void _synchronize_rcu_expedited(struct rcu_state *rsp, if (exp_funnel_lock(rsp, s)) return; /* Someone else did our work for us. */ - /* Marshall arguments and schedule the expedited grace period. */ - rew.rew_func = func; - rew.rew_rsp = rsp; - rew.rew_s = s; - INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); - schedule_work(&rew.rew_work); + /* 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(rsp, func, s); + } else { + /* Marshall arguments & schedule the expedited grace period. */ + rew.rew_func = func; + rew.rew_rsp = rsp; + rew.rew_s = s; + INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp); + schedule_work(&rew.rew_work); + } /* Wait for expedited grace period to complete. */ rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); @@ -676,6 +692,8 @@ void synchronize_rcu_expedited(void) { struct rcu_state *rsp = rcu_state_p; + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) + return; _synchronize_rcu_expedited(rsp, sync_rcu_exp_handler); } EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); @@ -693,3 +711,15 @@ void synchronize_rcu_expedited(void) EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +/* + * Switch to run-time mode once Tree RCU has fully initialized. + */ +static int __init rcu_exp_runtime_mode(void) +{ + rcu_test_sync_prims(); + rcu_scheduler_active = RCU_SCHEDULER_RUNNING; + rcu_test_sync_prims(); + return 0; +} +core_initcall(rcu_exp_runtime_mode); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 85c5a883c6e3..56583e764ebf 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -670,7 +670,7 @@ void synchronize_rcu(void) 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) + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return; if (rcu_gp_is_expedited()) synchronize_rcu_expedited(); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index f19271dce0a9..4f6db7e6a117 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -121,11 +121,14 @@ EXPORT_SYMBOL(rcu_read_lock_sched_held); * Should expedited grace-period primitives always fall back to their * non-expedited counterparts? Intended for use within RCU. Note * that if the user specifies both rcu_expedited and rcu_normal, then - * rcu_normal wins. + * rcu_normal wins. (Except during the time period during boot from + * when the first task is spawned until the rcu_exp_runtime_mode() + * core_initcall() is invoked, at which point everything is expedited.) */ bool rcu_gp_is_normal(void) { - return READ_ONCE(rcu_normal); + return READ_ONCE(rcu_normal) && + rcu_scheduler_active != RCU_SCHEDULER_INIT; } EXPORT_SYMBOL_GPL(rcu_gp_is_normal); @@ -135,13 +138,14 @@ static atomic_t rcu_expedited_nesting = /* * Should normal grace-period primitives be expedited? Intended for * use within RCU. Note that this function takes the rcu_expedited - * sysfs/boot variable into account as well as the rcu_expedite_gp() - * nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited() - * returns false is a -really- bad idea. + * sysfs/boot variable and rcu_scheduler_active into account as well + * as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp() + * until rcu_gp_is_expedited() returns false is a -really- bad idea. */ bool rcu_gp_is_expedited(void) { - return rcu_expedited || atomic_read(&rcu_expedited_nesting); + return rcu_expedited || atomic_read(&rcu_expedited_nesting) || + rcu_scheduler_active == RCU_SCHEDULER_INIT; } EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); @@ -257,7 +261,7 @@ EXPORT_SYMBOL_GPL(rcu_callback_map); int notrace debug_lockdep_rcu_enabled(void) { - return rcu_scheduler_active && debug_locks && + return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks && current->lockdep_recursion == 0; } EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); @@ -591,7 +595,7 @@ EXPORT_SYMBOL_GPL(call_rcu_tasks); void synchronize_rcu_tasks(void) { /* Complain if the scheduler has not started. */ - RCU_LOCKDEP_WARN(!rcu_scheduler_active, + RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE, "synchronize_rcu_tasks called too soon"); /* Wait for the grace period. */ @@ -813,6 +817,23 @@ static void rcu_spawn_tasks_kthread(void) #endif /* #ifdef CONFIG_TASKS_RCU */ +/* + * Test each non-SRCU synchronous grace-period wait API. This is + * useful just after a change in mode for these primitives, and + * during early boot. + */ +void rcu_test_sync_prims(void) +{ + if (!IS_ENABLED(CONFIG_PROVE_RCU)) + return; + synchronize_rcu(); + synchronize_rcu_bh(); + synchronize_sched(); + synchronize_rcu_expedited(); + synchronize_rcu_bh_expedited(); + synchronize_sched_expedited(); +} + #ifdef CONFIG_PROVE_RCU /* @@ -865,6 +886,7 @@ void rcu_early_boot_tests(void) early_boot_test_call_rcu_bh(); if (rcu_self_test_sched) early_boot_test_call_rcu_sched(); + rcu_test_sync_prims(); } static int rcu_verify_early_boot_tests(void) |