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/*
* Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance
*
* Original mutex implementation started by Ingo Molnar:
*
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Wound/wait implementation:
* Copyright (C) 2013 Canonical Ltd.
*
* Wound/ wait drop-in, actual wound-wait semantics and batching:
* Copyright (C) 2016-2018 VMWare Inc.
*
* This file contains the main data structure and API definitions.
*/
#ifndef _WW_MUTEX_H_
#define _WW_MUTEX_H_
#include "ww_mutex_test.h"
#include <linux/kernel.h>
#include <asm/atomic.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/spinlock.h>
struct ww_class {
spinlock_t lock;
atomic_long_t stamp;
struct lock_class_key acquire_key;
struct lock_class_key mutex_key;
const char *acquire_name;
const char *mutex_name;
bool is_wait_die;
};
struct ww_acquire_ctx {
struct ww_class *my_class;
unsigned long stamp;
unsigned long acquired;
u32 batched : 1;
u32 wounded : 1;
u32 done_acquire : 1;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
struct lockdep_map batch_map;
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
unsigned deadlock_inject_interval;
unsigned deadlock_inject_countdown;
#endif
};
struct ww_mutex {
struct mutex base;
struct ww_class *my_class;
wait_queue_head_t queue;
struct ww_acquire_ctx *ctx;
};
#define __WW_CLASS_INITIALIZER(ww_class) { \
.lock = __SPIN_LOCK_UNLOCKED(ww_class.lock), \
.stamp = ATOMIC_LONG_INIT(0), \
.acquire_name = #ww_class "_acquire", \
.mutex_name = #ww_class "_mutex", \
.is_wait_die = WW_WAITDIE, \
}
#define DEFINE_WW_CLASS(classname) \
struct ww_class classname = __WW_CLASS_INITIALIZER(classname)
#ifdef WW_BATCHING
void ww_acquire_batch_begin(struct ww_acquire_ctx *ctx);
void ww_acquire_batch_end(struct ww_acquire_ctx *ctx);
#else
#define ww_acquire_batch_begin(_a)
#define ww_acquire_batch_end(_a)
#endif
static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
struct ww_class *ww_class)
{
ctx->my_class = ww_class;
ctx->stamp = atomic_long_inc_return(&ww_class->stamp);
ctx->acquired = 0L;
ctx->batched = false;
ctx->wounded = false;
ctx->done_acquire = 0;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
lockdep_init_map(&ctx->dep_map, ww_class->acquire_name,
&ww_class->acquire_key, 0);
lockdep_init_map(&ctx->batch_map, ww_class->mutex_name,
&ww_class->mutex_key, 0);
lock_acquire(&ctx->dep_map, 0, 0, 0, 1, NULL, _RET_IP_);
lock_acquired(&ctx->dep_map, _RET_IP_);
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
ctx->deadlock_inject_interval = 1L;
ctx->deadlock_inject_countdown = ctx->stamp & 0x0f;
#endif
}
/**
* ww_acquire_done - marks the end of the acquire phase
* @ctx: the acquire context
*
* Marks the end of the acquire phase, any further w/w mutex lock calls using
* this context are forbidden.
*
* Calling this function is optional, it is just useful to document w/w mutex
* code and clearly designated the acquire phase from actually using the locked
* data structures.
*/
static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
{
#ifdef CONFIG_DEBUG_MUTEXES
lockdep_assert_held(ctx);
WARN_ON(ctx->batched);
DEBUG_LOCKS_WARN_ON(ctx->done_acquire);
#endif
ctx->done_acquire = 1;
}
/**
* ww_acquire_fini - releases a w/w acquire context
* @ctx: the acquire context to free
*
* Releases a w/w acquire context. This must be called _after_ all acquired w/w
* mutexes have been released with ww_mutex_unlock.
*/
static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
lock_release(&ctx->dep_map, 0, _THIS_IP_);
#endif
#ifdef CONFIG_DEBUG_MUTEXES
DEBUG_LOCKS_WARN_ON(ctx->acquired);
if (!IS_ENABLED(CONFIG_PROVE_LOCKING))
/*
* lockdep will normally handle this,
* but fail without anyway
*/
ctx->done_acquire = 1;
if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC))
/* ensure ww_acquire_fini will still fail if called twice */
ctx->acquired = ~0U;
#endif
}
static inline void ww_mutex_init(struct ww_mutex *ww,
struct ww_class *ww_class)
{
ww->my_class = ww_class;
ww->ctx = NULL;
init_waitqueue_head(&ww->queue);
mutex_init(&ww->base);
}
static inline bool ww_mutex_is_locked(struct ww_mutex *ww)
{
return mutex_is_locked(&ww->base);
}
int ww_mutex_trylock(struct ww_mutex *lock);
int ww_mutex_lock_interruptible(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx);
#define ww_mutex_lock_slow_interruptible ww_mutex_lock_interruptible
int ww_mutex_lock(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx);
#define ww_mutex_lock_slow ww_mutex_lock
void ww_mutex_unlock(struct ww_mutex *lock);
static inline void ww_mutex_destroy(struct ww_mutex *lock)
{
mutex_destroy(&lock->base);
}
#endif
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