blob: f41d2fb09f87bcd42147a388c3b2aa5fa1d91e9b [file] [log] [blame]
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tiny variant.
* 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
* 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
* Copyright (C) IBM Corporation, 2017
* Author: Paul McKenney <>
#include <linux/swait.h>
struct srcu_struct {
short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
short srcu_idx; /* Current reader array element. */
u8 srcu_gp_running; /* GP workqueue running? */
u8 srcu_gp_waiting; /* GP waiting for readers? */
struct swait_queue_head srcu_wq;
/* Last srcu_read_unlock() wakes GP. */
struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */
struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */
struct work_struct srcu_work; /* For driving grace periods. */
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
void srcu_drive_gp(struct work_struct *wp);
#define __SRCU_STRUCT_INIT(name, __ignored) \
{ \
.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
.srcu_cb_tail = &name.srcu_cb_head, \
.srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
* This odd _STATIC_ arrangement is needed for API compatibility with
* Tree SRCU, which needs some per-CPU data.
#define DEFINE_SRCU(name) \
struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
#define DEFINE_STATIC_SRCU(name) \
static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
void synchronize_srcu(struct srcu_struct *sp);
* Counts the new reader in the appropriate per-CPU element of the
* srcu_struct. Can be invoked from irq/bh handlers, but the matching
* __srcu_read_unlock() must be in the same handler instance. Returns an
* index that must be passed to the matching srcu_read_unlock().
static inline int __srcu_read_lock(struct srcu_struct *sp)
int idx;
idx = READ_ONCE(sp->srcu_idx);
WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1);
return idx;
static inline void synchronize_srcu_expedited(struct srcu_struct *sp)
static inline void srcu_barrier(struct srcu_struct *sp)
/* Defined here to avoid size increase for non-torture kernels. */
static inline void srcu_torture_stats_print(struct srcu_struct *sp,
char *tt, char *tf)
int idx;
idx = READ_ONCE(sp->srcu_idx) & 0x1;
pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
tt, tf, idx,