Quelle srcutiny.h Sprache: 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. */
u8 srcu_gp_running;  /* GP workqueue running? */
u8 srcu_gp_waiting;  /* GP waiting for readers? */
unsigned long srcu_idx;  /* Current reader array element in bit 0x2. */
unsigned long srcu_idx_max; /* Furthest future srcu_idx request. */
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, ___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, name)
#define DEFINE_STATIC_SRCU(name) \
static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)

// Dummy structure for srcu_notifier_head.
struct srcu_usage { };
#define __SRCU_USAGE_INIT(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;

preempt_disable();  // Needed for PREEMPT_LAZY
idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
preempt_enable();
return idx;
}

struct srcu_ctr;

static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp)
{
return (int)(intptr_t)(struct srcu_ctr __force __kernel *)scpp;
}

static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx)
{
return (struct srcu_ctr __percpu *)(intptr_t)idx;
}

static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp)
{
return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp));
}

static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp)
{
__srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp));
}

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);
}

#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0)
#define srcu_check_read_flavor_force(ssp, read_flavor) do { } while (0)

/* 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 = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n",
   tt, tf, idx,
   data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
   data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])),
   data_race(READ_ONCE(ssp->srcu_idx)),
   data_race(READ_ONCE(ssp->srcu_idx_max)));
}

#endif

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