linux-stable/include/linux/srcutiny.h
Paul E. McKenney 8c366db05b linux/srcu: Convert to SPDX license identifier
Replace the license boiler plate with a SPDX license identifier.
While in the area, update an email address.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Update ,h SPDX format per Joe Perches. ]
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
2019-02-09 08:45:59 -08:00

90 lines
2.6 KiB
C

/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tiny variant.
*
* Copyright (C) IBM Corporation, 2017
*
* Author: Paul McKenney <paulmck@linux.ibm.com>
*/
#ifndef _LINUX_SRCU_TINY_H
#define _LINUX_SRCU_TINY_H
#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. */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
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), \
__SRCU_DEP_MAP_INIT(name) \
}
/*
* 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 *ssp);
/*
* 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 *ssp)
{
int idx;
idx = READ_ONCE(ssp->srcu_idx);
WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1);
return idx;
}
static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)
{
synchronize_srcu(ssp);
}
static inline void srcu_barrier(struct srcu_struct *ssp)
{
synchronize_srcu(ssp);
}
/* Defined here to avoid size increase for non-torture kernels. */
static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
char *tt, char *tf)
{
int idx;
idx = READ_ONCE(ssp->srcu_idx) & 0x1;
pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
tt, tf, idx,
READ_ONCE(ssp->srcu_lock_nesting[!idx]),
READ_ONCE(ssp->srcu_lock_nesting[idx]));
}
#endif