EXPORT_SYMBOL(mutex_lock);
#endif
-static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
- struct ww_acquire_ctx *ww_ctx)
+static __always_inline void
+ww_mutex_lock_acquired(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
{
#ifdef CONFIG_DEBUG_MUTEXES
/*
(a->stamp != b->stamp || a > b);
}
+/*
+ * Wake up any waiters that may have to back off when the lock is held by the
+ * given context.
+ *
+ * Due to the invariants on the wait list, this can only affect the first
+ * waiter with a context.
+ *
+ * The current task must not be on the wait list.
+ */
+static void __sched
+__ww_mutex_wakeup_for_backoff(struct mutex *lock, struct ww_acquire_ctx *ww_ctx)
+{
+ struct mutex_waiter *cur;
+
+ lockdep_assert_held(&lock->wait_lock);
+
+ list_for_each_entry(cur, &lock->wait_list, list) {
+ if (!cur->ww_ctx)
+ continue;
+
+ if (cur->ww_ctx->acquired > 0 &&
+ __ww_ctx_stamp_after(cur->ww_ctx, ww_ctx)) {
+ debug_mutex_wake_waiter(lock, cur);
+ wake_up_process(cur->task);
+ }
+
+ break;
+ }
+}
+
/*
* After acquiring lock with fastpath or when we lost out in contested
* slowpath, set ctx and wake up any waiters so they can recheck.
*/
static __always_inline void
-ww_mutex_set_context_fastpath(struct ww_mutex *lock,
- struct ww_acquire_ctx *ctx)
+ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
- unsigned long flags;
- struct mutex_waiter *cur;
-
ww_mutex_lock_acquired(lock, ctx);
lock->ctx = ctx;
* Uh oh, we raced in fastpath, wake up everyone in this case,
* so they can see the new lock->ctx.
*/
- spin_lock_mutex(&lock->base.wait_lock, flags);
- list_for_each_entry(cur, &lock->base.wait_list, list) {
- debug_mutex_wake_waiter(&lock->base, cur);
- wake_up_process(cur->task);
- }
- spin_unlock_mutex(&lock->base.wait_lock, flags);
+ spin_lock(&lock->base.wait_lock);
+ __ww_mutex_wakeup_for_backoff(&lock->base, ctx);
+ spin_unlock(&lock->base.wait_lock);
}
/*
- * After acquiring lock in the slowpath set ctx and wake up any
- * waiters so they can recheck.
+ * After acquiring lock in the slowpath set ctx.
+ *
+ * Unlike for the fast path, the caller ensures that waiters are woken up where
+ * necessary.
*
* Callers must hold the mutex wait_lock.
*/
static __always_inline void
-ww_mutex_set_context_slowpath(struct ww_mutex *lock,
- struct ww_acquire_ctx *ctx)
+ww_mutex_set_context_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
- struct mutex_waiter *cur;
-
ww_mutex_lock_acquired(lock, ctx);
lock->ctx = ctx;
+}
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+
+static inline
+bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
+ struct mutex_waiter *waiter)
+{
+ struct ww_mutex *ww;
+
+ ww = container_of(lock, struct ww_mutex, base);
/*
- * Give any possible sleeping processes the chance to wake up,
- * so they can recheck if they have to back off.
+ * If ww->ctx is set the contents are undefined, only
+ * by acquiring wait_lock there is a guarantee that
+ * they are not invalid when reading.
+ *
+ * As such, when deadlock detection needs to be
+ * performed the optimistic spinning cannot be done.
+ *
+ * Check this in every inner iteration because we may
+ * be racing against another thread's ww_mutex_lock.
*/
- list_for_each_entry(cur, &lock->base.wait_list, list) {
- debug_mutex_wake_waiter(&lock->base, cur);
- wake_up_process(cur->task);
- }
+ if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))
+ return false;
+
+ /*
+ * If we aren't on the wait list yet, cancel the spin
+ * if there are waiters. We want to avoid stealing the
+ * lock from a waiter with an earlier stamp, since the
+ * other thread may already own a lock that we also
+ * need.
+ */
+ if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))
+ return false;
+
+ /*
+ * Similarly, stop spinning if we are no longer the
+ * first waiter.
+ */
+ if (waiter && !__mutex_waiter_is_first(lock, waiter))
+ return false;
+
+ return true;
}
-#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
- * Look out! "owner" is an entirely speculative pointer
- * access and not reliable.
+ * Look out! "owner" is an entirely speculative pointer access and not
+ * reliable.
+ *
+ * "noinline" so that this function shows up on perf profiles.
*/
static noinline
-bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner,
+ struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter)
{
bool ret = true;
break;
}
+ if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) {
+ ret = false;
+ break;
+ }
+
cpu_relax();
}
rcu_read_unlock();
* with the spinner at the head of the OSQ, if present, until the owner is
* changed to itself.
*/
-static bool mutex_optimistic_spin(struct mutex *lock,
- struct ww_acquire_ctx *ww_ctx,
- const bool use_ww_ctx, const bool waiter)
+static __always_inline bool
+mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
+ const bool use_ww_ctx, struct mutex_waiter *waiter)
{
if (!waiter) {
/*
for (;;) {
struct task_struct *owner;
- if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) {
- struct ww_mutex *ww;
-
- ww = container_of(lock, struct ww_mutex, base);
- /*
- * If ww->ctx is set the contents are undefined, only
- * by acquiring wait_lock there is a guarantee that
- * they are not invalid when reading.
- *
- * As such, when deadlock detection needs to be
- * performed the optimistic spinning cannot be done.
- */
- if (READ_ONCE(ww->ctx))
- goto fail_unlock;
- }
-
/* Try to acquire the mutex... */
owner = __mutex_trylock_or_owner(lock);
if (!owner)
* There's an owner, wait for it to either
* release the lock or go to sleep.
*/
- if (!mutex_spin_on_owner(lock, owner))
+ if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter))
goto fail_unlock;
/*
return false;
}
#else
-static bool mutex_optimistic_spin(struct mutex *lock,
- struct ww_acquire_ctx *ww_ctx,
- const bool use_ww_ctx, const bool waiter)
+static __always_inline bool
+mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
+ const bool use_ww_ctx, struct mutex_waiter *waiter)
{
return false;
}
EXPORT_SYMBOL(ww_mutex_unlock);
static inline int __sched
-__ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
+__ww_mutex_lock_check_stamp(struct mutex *lock, struct mutex_waiter *waiter,
+ struct ww_acquire_ctx *ctx)
{
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
+ struct mutex_waiter *cur;
- if (!hold_ctx)
- return 0;
+ if (hold_ctx && __ww_ctx_stamp_after(ctx, hold_ctx))
+ goto deadlock;
- if (__ww_ctx_stamp_after(ctx, hold_ctx)) {
-#ifdef CONFIG_DEBUG_MUTEXES
- DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
- ctx->contending_lock = ww;
-#endif
- return -EDEADLK;
+ /*
+ * If there is a waiter in front of us that has a context, then its
+ * stamp is earlier than ours and we must back off.
+ */
+ cur = waiter;
+ list_for_each_entry_continue_reverse(cur, &lock->wait_list, list) {
+ if (cur->ww_ctx)
+ goto deadlock;
}
return 0;
+
+deadlock:
+#ifdef CONFIG_DEBUG_MUTEXES
+ DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
+ ctx->contending_lock = ww;
+#endif
+ return -EDEADLK;
}
static inline int __sched
}
pos = &cur->list;
+
+ /*
+ * Wake up the waiter so that it gets a chance to back
+ * off.
+ */
+ if (cur->ww_ctx->acquired > 0) {
+ debug_mutex_wake_waiter(lock, cur);
+ wake_up_process(cur->task);
+ }
}
list_add_tail(&waiter->list, pos);
struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
struct mutex_waiter waiter;
- unsigned long flags;
bool first = false;
struct ww_mutex *ww;
int ret;
- ww = container_of(lock, struct ww_mutex, base);
+ might_sleep();
+ ww = container_of(lock, struct ww_mutex, base);
if (use_ww_ctx && ww_ctx) {
if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
return -EALREADY;
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
if (__mutex_trylock(lock) ||
- mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, false)) {
+ mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) {
/* got the lock, yay! */
lock_acquired(&lock->dep_map, ip);
if (use_ww_ctx && ww_ctx)
return 0;
}
- spin_lock_mutex(&lock->wait_lock, flags);
+ spin_lock(&lock->wait_lock);
/*
* After waiting to acquire the wait_lock, try again.
*/
- if (__mutex_trylock(lock))
+ if (__mutex_trylock(lock)) {
+ if (use_ww_ctx && ww_ctx)
+ __ww_mutex_wakeup_for_backoff(lock, ww_ctx);
+
goto skip_wait;
+ }
debug_mutex_lock_common(lock, &waiter);
debug_mutex_add_waiter(lock, &waiter, current);
if (!use_ww_ctx) {
/* add waiting tasks to the end of the waitqueue (FIFO): */
list_add_tail(&waiter.list, &lock->wait_list);
+
+#ifdef CONFIG_DEBUG_MUTEXES
+ waiter.ww_ctx = MUTEX_POISON_WW_CTX;
+#endif
} else {
/* Add in stamp order, waking up waiters that must back off. */
ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
}
if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) {
- ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
+ ret = __ww_mutex_lock_check_stamp(lock, &waiter, ww_ctx);
if (ret)
goto err;
}
- spin_unlock_mutex(&lock->wait_lock, flags);
+ spin_unlock(&lock->wait_lock);
schedule_preempt_disabled();
/*
* or we must see its unlock and acquire.
*/
if (__mutex_trylock(lock) ||
- (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, true)))
+ (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter)))
break;
- spin_lock_mutex(&lock->wait_lock, flags);
+ spin_lock(&lock->wait_lock);
}
- spin_lock_mutex(&lock->wait_lock, flags);
+ spin_lock(&lock->wait_lock);
acquired:
__set_current_state(TASK_RUNNING);
if (use_ww_ctx && ww_ctx)
ww_mutex_set_context_slowpath(ww, ww_ctx);
- spin_unlock_mutex(&lock->wait_lock, flags);
+ spin_unlock(&lock->wait_lock);
preempt_enable();
return 0;
__set_current_state(TASK_RUNNING);
mutex_remove_waiter(lock, &waiter, current);
err_early_backoff:
- spin_unlock_mutex(&lock->wait_lock, flags);
+ spin_unlock(&lock->wait_lock);
debug_mutex_free_waiter(&waiter);
mutex_release(&lock->dep_map, 1, ip);
preempt_enable();
return ret;
}
+static int __sched
+__mutex_lock(struct mutex *lock, long state, unsigned int subclass,
+ struct lockdep_map *nest_lock, unsigned long ip)
+{
+ return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
+}
+
+static int __sched
+__ww_mutex_lock(struct mutex *lock, long state, unsigned int subclass,
+ struct lockdep_map *nest_lock, unsigned long ip,
+ struct ww_acquire_ctx *ww_ctx)
+{
+ return __mutex_lock_common(lock, state, subclass, nest_lock, ip, ww_ctx, true);
+}
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void __sched
mutex_lock_nested(struct mutex *lock, unsigned int subclass)
{
- might_sleep();
- __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
- subclass, NULL, _RET_IP_, NULL, 0);
+ __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_nested);
void __sched
_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
{
- might_sleep();
- __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
- 0, nest, _RET_IP_, NULL, 0);
+ __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
}
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
int __sched
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
{
- might_sleep();
- return __mutex_lock_common(lock, TASK_KILLABLE,
- subclass, NULL, _RET_IP_, NULL, 0);
+ return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
int __sched
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
- might_sleep();
- return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
- subclass, NULL, _RET_IP_, NULL, 0);
+ return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
}
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
+void __sched
+mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
+{
+ int token;
+
+ might_sleep();
+
+ token = io_schedule_prepare();
+ __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
+ subclass, NULL, _RET_IP_, NULL, 0);
+ io_schedule_finish(token);
+}
+EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
+
static inline int
ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
int ret;
might_sleep();
- ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
- 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
- ctx, 1);
+ ret = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,
+ 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
+ ctx);
if (!ret && ctx && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
int ret;
might_sleep();
- ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
- 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
- ctx, 1);
+ ret = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,
+ 0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
+ ctx);
if (!ret && ctx && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
{
struct task_struct *next = NULL;
- unsigned long owner, flags;
DEFINE_WAKE_Q(wake_q);
+ unsigned long owner;
mutex_release(&lock->dep_map, 1, ip);
owner = old;
}
- spin_lock_mutex(&lock->wait_lock, flags);
+ spin_lock(&lock->wait_lock);
debug_mutex_unlock(lock);
if (!list_empty(&lock->wait_list)) {
/* get the first entry from the wait-list: */
if (owner & MUTEX_FLAG_HANDOFF)
__mutex_handoff(lock, next);
- spin_unlock_mutex(&lock->wait_lock, flags);
+ spin_unlock(&lock->wait_lock);
wake_up_q(&wake_q);
}
}
EXPORT_SYMBOL(mutex_lock_killable);
+void __sched mutex_lock_io(struct mutex *lock)
+{
+ int token;
+
+ token = io_schedule_prepare();
+ mutex_lock(lock);
+ io_schedule_finish(token);
+}
+EXPORT_SYMBOL_GPL(mutex_lock_io);
+
static noinline void __sched
__mutex_lock_slowpath(struct mutex *lock)
{
- __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
- NULL, _RET_IP_, NULL, 0);
+ __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
}
static noinline int __sched
__mutex_lock_killable_slowpath(struct mutex *lock)
{
- return __mutex_lock_common(lock, TASK_KILLABLE, 0,
- NULL, _RET_IP_, NULL, 0);
+ return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
}
static noinline int __sched
__mutex_lock_interruptible_slowpath(struct mutex *lock)
{
- return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
- NULL, _RET_IP_, NULL, 0);
+ return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
}
static noinline int __sched
__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
- return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
- NULL, _RET_IP_, ctx, 1);
+ return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, NULL,
+ _RET_IP_, ctx);
}
static noinline int __sched
__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx)
{
- return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
- NULL, _RET_IP_, ctx, 1);
+ return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, NULL,
+ _RET_IP_, ctx);
}
#endif
projects / linux.git / blobdiff