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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tree variant.
*
* Copyright (C) IBM Corporation, 2017
*
* Author: Paul McKenney <paulmck@linux.ibm.com>
*/
#ifndef _LINUX_SRCU_TREE_H
#define _LINUX_SRCU_TREE_H
#include <linux/rcu_node_tree.h>
#include <linux/completion.h>
struct srcu_node;
struct srcu_struct;
/*
* Per-CPU structure feeding into leaf srcu_node, similar in function
* to rcu_node.
*/
struct srcu_data {
/* Read-side state. */
atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */
atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */
int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */
/* Update-side state. */
spinlock_t __private lock ____cacheline_internodealigned_in_smp;
struct rcu_segcblist srcu_cblist; /* List of callbacks.*/
unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */
unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
bool srcu_cblist_invoking; /* Invoking these CBs? */
struct timer_list delay_work; /* Delay for CB invoking */
struct work_struct work; /* Context for CB invoking. */
struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */
struct srcu_node *mynode; /* Leaf srcu_node. */
unsigned long grpmask; /* Mask for leaf srcu_node */
/* ->srcu_data_have_cbs[]. */
int cpu;
struct srcu_struct *ssp;
};
/*
* Node in SRCU combining tree, similar in function to rcu_data.
*/
struct srcu_node {
spinlock_t __private lock;
unsigned long srcu_have_cbs[4]; /* GP seq for children having CBs, but only */
/* if greater than ->srcu_gp_seq. */
unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs have CBs for given GP? */
unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
struct srcu_node *srcu_parent; /* Next up in tree. */
int grplo; /* Least CPU for node. */
int grphi; /* Biggest CPU for node. */
};
/*
* Per-SRCU-domain structure, update-side data linked from srcu_struct.
*/
struct srcu_usage {
struct srcu_node *node; /* Combining tree. */
struct srcu_node *level[RCU_NUM_LVLS + 1];
/* First node at each level. */
int srcu_size_state; /* Small-to-big transition state. */
struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
spinlock_t __private lock; /* Protect counters and size state. */
struct mutex srcu_gp_mutex; /* Serialize GP work. */
unsigned long srcu_gp_seq; /* Grace-period seq #. */
unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */
unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
unsigned long srcu_gp_start; /* Last GP start timestamp (jiffies) */
unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */
unsigned long srcu_size_jiffies; /* Current contention-measurement interval. */
unsigned long srcu_n_lock_retries; /* Contention events in current interval. */
unsigned long srcu_n_exp_nodelay; /* # expedited no-delays in current GP phase. */
bool sda_is_static; /* May ->sda be passed to free_percpu()? */
unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */
struct completion srcu_barrier_completion;
/* Awaken barrier rq at end. */
atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */
/* callback for the barrier */
/* operation. */
unsigned long reschedule_jiffies;
unsigned long reschedule_count;
struct delayed_work work;
struct srcu_struct *srcu_ssp;
};
/*
* Per-SRCU-domain structure, similar in function to rcu_state.
*/
struct srcu_struct {
unsigned int srcu_idx; /* Current rdr array element. */
struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
struct lockdep_map dep_map;
struct srcu_usage *srcu_sup; /* Update-side data. */
};
// Values for size state variable (->srcu_size_state). Once the state
// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
// this state machine one step per grace period until the SRCU_SIZE_BIG state
// is reached. Otherwise, the state machine remains in the SRCU_SIZE_SMALL
// state indefinitely.
#define SRCU_SIZE_SMALL 0 // No srcu_node combining tree, ->node == NULL
#define SRCU_SIZE_ALLOC 1 // An srcu_node tree is being allocated, initialized,
// and then referenced by ->node. It will not be used.
#define SRCU_SIZE_WAIT_BARRIER 2 // The srcu_node tree starts being used by everything
// except call_srcu(), especially by srcu_barrier().
// By the end of this state, all CPUs and threads
// are aware of this tree's existence.
#define SRCU_SIZE_WAIT_CALL 3 // The srcu_node tree starts being used by call_srcu().
// By the end of this state, all of the call_srcu()
// invocations that were running on a non-boot CPU
// and using the boot CPU's callback queue will have
// completed.
#define SRCU_SIZE_WAIT_CBS1 4 // Don't trust the ->srcu_have_cbs[] grace-period
#define SRCU_SIZE_WAIT_CBS2 5 // sequence elements or the ->srcu_data_have_cbs[]
#define SRCU_SIZE_WAIT_CBS3 6 // CPU-bitmask elements until all four elements of
#define SRCU_SIZE_WAIT_CBS4 7 // each array have been initialized.
#define SRCU_SIZE_BIG 8 // The srcu_node combining tree is fully initialized
// and all aspects of it are being put to use.
/* Values for state variable (bottom bits of ->srcu_gp_seq). */
#define SRCU_STATE_IDLE 0
#define SRCU_STATE_SCAN1 1
#define SRCU_STATE_SCAN2 2
/*
* Values for initializing gp sequence fields. Higher values allow wrap arounds to
* occur earlier.
* The second value with state is useful in the case of static initialization of
* srcu_usage where srcu_gp_seq_needed is expected to have some state value in its
* lower bits (or else it will appear to be already initialized within
* the call check_init_srcu_struct()).
*/
#define SRCU_GP_SEQ_INITIAL_VAL ((0UL - 100UL) << RCU_SEQ_CTR_SHIFT)
#define SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE (SRCU_GP_SEQ_INITIAL_VAL - 1)
#define __SRCU_USAGE_INIT(name) \
{ \
.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
.srcu_gp_seq = SRCU_GP_SEQ_INITIAL_VAL, \
.srcu_gp_seq_needed = SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE, \
.srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL, \
.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \
}
#define __SRCU_STRUCT_INIT_COMMON(name, usage_name) \
.srcu_sup = &usage_name, \
__SRCU_DEP_MAP_INIT(name)
#define __SRCU_STRUCT_INIT_MODULE(name, usage_name) \
{ \
__SRCU_STRUCT_INIT_COMMON(name, usage_name) \
}
#define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name) \
{ \
.sda = &pcpu_name, \
__SRCU_STRUCT_INIT_COMMON(name, usage_name) \
}
/*
* Define and initialize a srcu struct at build time.
* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
*
* Note that although DEFINE_STATIC_SRCU() hides the name from other
* files, the per-CPU variable rules nevertheless require that the
* chosen name be globally unique. These rules also prohibit use of
* DEFINE_STATIC_SRCU() within a function. If these rules are too
* restrictive, declare the srcu_struct manually. For example, in
* each file:
*
* static struct srcu_struct my_srcu;
*
* Then, before the first use of each my_srcu, manually initialize it:
*
* init_srcu_struct(&my_srcu);
*
* See include/linux/percpu-defs.h for the rules on per-CPU variables.
*/
#ifdef MODULE
# define __DEFINE_SRCU(name, is_static) \
static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \
is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage); \
extern struct srcu_struct * const __srcu_struct_##name; \
struct srcu_struct * const __srcu_struct_##name \
__section("___srcu_struct_ptrs") = &name
#else
# define __DEFINE_SRCU(name, is_static) \
static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \
static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \
is_static struct srcu_struct name = \
__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
#endif
#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
void synchronize_srcu_expedited(struct srcu_struct *ssp);
void srcu_barrier(struct srcu_struct *ssp);
void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
#endif
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