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#include "core/ww_mutex.h"
/*
* A lightweight ww_mutex implemenentation for backwards compat, based
* on the old TTM reservation implementation. There are less tests and
* There may, in theory, be starvation in context-free locks, and there
* may be a slight performance loss in contended cases, since none of the
* mutex subsystem contended case optimizations are present.
*
* The API and lockdep annotation is Copyright (C) 2013, Canonical Ltd. (GPL)
* The implementation itself, except the lockdep annotation,
* should be considered available under the same license as TTM.
*/
static bool __wwl_mutex_lock(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx,
int *err)
{
WARN_ON(ctx && ctx->contending_lock &&
ctx->contending_lock != lock);
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
if (ctx && ctx->count == ctx->deadlock_injection) {
ctx->deadlock_injection *= 2;
ctx->count = 0;
if (ctx->contending_lock != lock) {
ctx->contending_lock = lock;
*err = -EDEADLK;
return true;
}
}
#endif
spin_lock(&lock->my_class->lock);
if (!lock->held) {
lock->held = true;
lock->holder = ctx;
spin_unlock(&lock->my_class->lock);
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
if (ctx)
ctx->count++;
#endif
if (ctx && ctx->contending_lock == lock)
ctx->contending_lock = NULL;
*err = 0;
return true;
} else if (ctx && lock->holder == ctx) {
spin_unlock(&lock->my_class->lock);
*err = -EALREADY;
return true;
} else if (ctx && ctx->contending_lock != lock &&
lock->holder &&
lock->holder->ticket < ctx->ticket) {
spin_unlock(&lock->my_class->lock);
ctx->contending_lock = lock;
*err = -EDEADLK;
return true;
}
spin_unlock(&lock->my_class->lock);
return false;
}
int ww_mutex_trylock(struct ww_mutex *lock)
{
bool acquired;
int err = -EBUSY;
lock_acquire(&lock->base.dep_map, 0, 1, 0, 1, NULL, _RET_IP_);
acquired = __wwl_mutex_lock(lock, NULL, &err);
if (acquired)
lock_acquired(&lock->base.dep_map, _RET_IP_);
else
lock_release(&lock->base.dep_map, 0, _RET_IP_);
return acquired ? 1 : 0;
}
int ww_mutex_lock_interruptible(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx)
{
int err = -EINTR;
lock_acquire(&lock->base.dep_map, 0, 0, 0, 1,
ctx ? &ctx->dep_map : NULL, _RET_IP_);
if (!__wwl_mutex_lock(lock, ctx, &err)) {
lock_contended(&lock->base.dep_map, _RET_IP_);
wait_event_interruptible(lock->queue,
__wwl_mutex_lock(lock, ctx, &err));
}
if (!err) {
lock_acquired(&lock->base.dep_map, _RET_IP_);
} else {
lock_contended(&lock->base.dep_map, _RET_IP_);
lock_release(&lock->base.dep_map, 0, _RET_IP_);
}
return err;
}
int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
int err = -EBUSY;
lock_acquire(&lock->base.dep_map, 0, 0, 0, 1,
ctx ? &ctx->dep_map : NULL, _RET_IP_);
if (!__wwl_mutex_lock(lock, ctx, &err)) {
lock_contended(&lock->base.dep_map, _RET_IP_);
wait_event(lock->queue, __wwl_mutex_lock(lock, ctx, &err));
}
if (!err) {
lock_acquired(&lock->base.dep_map, _RET_IP_);
} else {
lock_contended(&lock->base.dep_map, _RET_IP_);
lock_release(&lock->base.dep_map, 0, _RET_IP_);
}
WARN_ON_ONCE(err == -EBUSY);
return err;
}
void ww_mutex_unlock(struct ww_mutex *lock)
{
lock_release(&lock->base.dep_map, 0, _RET_IP_);
spin_lock(&lock->my_class->lock);
lock->held = false;
lock->holder = NULL;
wake_up_all(&lock->queue);
spin_unlock(&lock->my_class->lock);
}
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