/**
* rt_mutex_start_proxy_lock() - Start lock acquisition for another task
* @lock: the rt_mutex to take
* @waiter: the pre-initialized rt_mutex_waiter
* @task: the task to prepare
* @detect_deadlock: perform deadlock detection (1) or not (0)
*
* Returns:
* 0 - task blocked on lock
* 1 - acquired the lock for task, caller should wake it up
* <0 - error
*
* Special API call for FUTEX_REQUEUE_PI support.
*/
int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
struct rt_mutex_waiter *waiter,
struct task_struct *task, int detect_deadlock)
{
int ret;
raw_spin_lock(&lock->wait_lock);
if (try_to_take_rt_mutex(lock, task, NULL)) {
raw_spin_unlock(&lock->wait_lock);
return 1;
}
ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
if (ret && !rt_mutex_owner(lock)) {
/*
* Reset the return value. We might have
* returned with -EDEADLK and the owner
* released the lock while we were walking the
* pi chain. Let the waiter sort it out.
*/
ret = 0;
}
if (unlikely(ret))
remove_waiter(lock, waiter);
raw_spin_unlock(&lock->wait_lock);
debug_rt_mutex_print_deadlock(waiter);
return ret;
}
/*
* Slow path try-lock function:
*/
static inline int rt_mutex_slowtrylock(struct rt_mutex *lock)
{
int ret;
/*
* If the lock already has an owner we fail to get the lock.
* This can be done without taking the @lock->wait_lock as
* it is only being read, and this is a trylock anyway.
*/
if (rt_mutex_owner(lock))
return 0;
/*
* The mutex has currently no owner. Lock the wait lock and
* try to acquire the lock.
*/
raw_spin_lock(&lock->wait_lock);
ret = try_to_take_rt_mutex(lock, current, NULL);
/*
* try_to_take_rt_mutex() sets the lock waiters bit
* unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock(&lock->wait_lock);
return ret;
}
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
int detect_deadlock)
{
struct rt_mutex_waiter waiter;
int ret = 0;
debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
raw_spin_lock(&lock->wait_lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock)) {
raw_spin_unlock(&lock->wait_lock);
return 0;
}
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout)) {
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&timeout->timer))
timeout->task = NULL;
}
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter,
detect_deadlock);
set_current_state(TASK_RUNNING);
if (unlikely(waiter.task))
remove_waiter(lock, &waiter);
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock(&lock->wait_lock);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
/*
* Readjust priority, when we did not get the lock. We might
* have been the pending owner and boosted. Since we did not
* take the lock, the PI boost has to go.
*/
if (unlikely(ret))
rt_mutex_adjust_prio(current);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
int detect_deadlock)
{
struct rt_mutex_waiter waiter;
int ret = 0;
debug_rt_mutex_init_waiter(&waiter);
RB_CLEAR_NODE(&waiter.pi_tree_entry);
RB_CLEAR_NODE(&waiter.tree_entry);
raw_spin_lock(&lock->wait_lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock, current, NULL)) {
raw_spin_unlock(&lock->wait_lock);
return 0;
}
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout)) {
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&timeout->timer))
timeout->task = NULL;
}
ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock);
if (likely(!ret))
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
set_current_state(TASK_RUNNING);
if (unlikely(ret))
remove_waiter(lock, &waiter);
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock(&lock->wait_lock);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}
/**
* __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
* @lock: the rt_mutex to take
* @state: the state the task should block in (TASK_INTERRUPTIBLE
* or TASK_UNINTERRUPTIBLE)
* @timeout: the pre-initialized and started timer, or NULL for none
* @waiter: the pre-initialized rt_mutex_waiter
*
* lock->wait_lock must be held by the caller.
*/
static int __sched
__rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
struct rt_mutex_waiter *waiter)
{
int ret = 0;
int was_disabled;
for (;;) {
/* Try to acquire the lock: */
if (try_to_take_rt_mutex(lock, current, waiter))
break;
/*
* TASK_INTERRUPTIBLE checks for signals and
* timeout. Ignored otherwise.
*/
if (unlikely(state == TASK_INTERRUPTIBLE)) {
/* Signal pending? */
if (signal_pending(current))
ret = -EINTR;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
if (ret)
break;
}
raw_spin_unlock(&lock->wait_lock);
was_disabled = irqs_disabled();
if (was_disabled)
local_irq_enable();
debug_rt_mutex_print_deadlock(waiter);
schedule_rt_mutex(lock);
if (was_disabled)
local_irq_disable();
raw_spin_lock(&lock->wait_lock);
set_current_state(state);
}
return ret;
}
/*
* Slow path try-lock function:
*/
static inline int
rt_mutex_slowtrylock(struct rt_mutex *lock)
{
int ret = 0;
raw_spin_lock(&lock->wait_lock);
if (likely(rt_mutex_owner(lock) != current)) {
ret = try_to_take_rt_mutex(lock, current, NULL);
/*
* try_to_take_rt_mutex() sets the lock waiters
* bit unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
}
raw_spin_unlock(&lock->wait_lock);
return ret;
}
/*
* Slow path try-lock function:
*/
static inline int
rt_mutex_slowtrylock(struct rt_mutex *lock)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&lock->wait_lock, flags);
if (likely(rt_mutex_owner(lock) != current)) {
init_lists(lock);
ret = try_to_take_rt_mutex(lock);
/*
* try_to_take_rt_mutex() sets the lock waiters
* bit unconditionally. Clean this up.
*/
fixup_rt_mutex_waiters(lock);
}
spin_unlock_irqrestore(&lock->wait_lock, flags);
return ret;
}
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
int detect_deadlock)
{
int ret = 0, saved_lock_depth = -1;
struct rt_mutex_waiter waiter;
unsigned long flags;
debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
spin_lock_irqsave(&lock->wait_lock, flags);
init_lists(lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock)) {
spin_unlock_irqrestore(&lock->wait_lock, flags);
return 0;
}
/*
* We drop the BKL here before we go into the wait loop to avoid a
* possible deadlock in the scheduler.
*/
if (unlikely(current->lock_depth >= 0))
saved_lock_depth = rt_release_bkl(lock, flags);
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout))
hrtimer_start(&timeout->timer, timeout->timer.expires,
HRTIMER_MODE_ABS);
for (;;) {
unsigned long saved_flags;
/* Try to acquire the lock: */
if (try_to_take_rt_mutex(lock))
break;
/*
* TASK_INTERRUPTIBLE checks for signals and
* timeout. Ignored otherwise.
*/
if (unlikely(state == TASK_INTERRUPTIBLE)) {
/* Signal pending? */
if (signal_pending(current))
ret = -EINTR;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
if (ret)
break;
}
/*
* waiter.task is NULL the first time we come here and
* when we have been woken up by the previous owner
* but the lock got stolen by a higher prio task.
*/
if (!waiter.task) {
ret = task_blocks_on_rt_mutex(lock, &waiter,
detect_deadlock, flags);
/*
* If we got woken up by the owner then start loop
* all over without going into schedule to try
* to get the lock now:
*/
if (unlikely(!waiter.task))
continue;
if (unlikely(ret))
break;
}
saved_flags = current->flags & PF_NOSCHED;
current->flags &= ~PF_NOSCHED;
spin_unlock_irq(&lock->wait_lock);
debug_rt_mutex_print_deadlock(&waiter);
if (waiter.task)
schedule_rt_mutex(lock);
spin_lock_irq(&lock->wait_lock);
current->flags |= saved_flags;
set_current_state(state);
}
set_current_state(TASK_RUNNING);
if (unlikely(waiter.task))
remove_waiter(lock, &waiter, flags);
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
spin_unlock_irqrestore(&lock->wait_lock, flags);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
/*
* Readjust priority, when we did not get the lock. We might
* have been the pending owner and boosted. Since we did not
* take the lock, the PI boost has to go.
*/
if (unlikely(ret))
rt_mutex_adjust_prio(current);
/* Must we reaquire the BKL? */
if (unlikely(saved_lock_depth >= 0))
rt_reacquire_bkl(saved_lock_depth);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}
/*
* Slow path lock function spin_lock style: this variant is very
* careful not to miss any non-lock wakeups.
*
* The wakeup side uses wake_up_process_mutex, which, combined with
* the xchg code of this function is a transparent sleep/wakeup
* mechanism nested within any existing sleep/wakeup mechanism. This
* enables the seemless use of arbitrary (blocking) spinlocks within
* sleep/wakeup event loops.
*/
static void fastcall noinline __sched
rt_spin_lock_slowlock(struct rt_mutex *lock)
{
struct rt_mutex_waiter waiter;
unsigned long saved_state, state, flags;
debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
spin_lock_irqsave(&lock->wait_lock, flags);
init_lists(lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock)) {
spin_unlock_irqrestore(&lock->wait_lock, flags);
return;
}
BUG_ON(rt_mutex_owner(lock) == current);
/*
* Here we save whatever state the task was in originally,
* we'll restore it at the end of the function and we'll take
* any intermediate wakeup into account as well, independently
* of the lock sleep/wakeup mechanism. When we get a real
* wakeup the task->state is TASK_RUNNING and we change
* saved_state accordingly. If we did not get a real wakeup
* then we return with the saved state.
*/
saved_state = xchg(¤t->state, TASK_UNINTERRUPTIBLE);
for (;;) {
unsigned long saved_flags;
int saved_lock_depth = current->lock_depth;
/* Try to acquire the lock */
if (try_to_take_rt_mutex(lock))
break;
/*
* waiter.task is NULL the first time we come here and
* when we have been woken up by the previous owner
* but the lock got stolen by an higher prio task.
*/
if (!waiter.task) {
task_blocks_on_rt_mutex(lock, &waiter, 0, flags);
/* Wakeup during boost ? */
if (unlikely(!waiter.task))
continue;
}
/*
* Prevent schedule() to drop BKL, while waiting for
* the lock ! We restore lock_depth when we come back.
*/
saved_flags = current->flags & PF_NOSCHED;
current->lock_depth = -1;
current->flags &= ~PF_NOSCHED;
spin_unlock_irqrestore(&lock->wait_lock, flags);
debug_rt_mutex_print_deadlock(&waiter);
schedule_rt_mutex(lock);
spin_lock_irqsave(&lock->wait_lock, flags);
current->flags |= saved_flags;
current->lock_depth = saved_lock_depth;
state = xchg(¤t->state, TASK_UNINTERRUPTIBLE);
if (unlikely(state == TASK_RUNNING))
saved_state = TASK_RUNNING;
}
state = xchg(¤t->state, saved_state);
if (unlikely(state == TASK_RUNNING))
current->state = TASK_RUNNING;
/*
* Extremely rare case, if we got woken up by a non-mutex wakeup,
* and we managed to steal the lock despite us not being the
* highest-prio waiter (due to SCHED_OTHER changing prio), then we
* can end up with a non-NULL waiter.task:
*/
if (unlikely(waiter.task))
remove_waiter(lock, &waiter, flags);
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up:
*/
fixup_rt_mutex_waiters(lock);
spin_unlock_irqrestore(&lock->wait_lock, flags);
debug_rt_mutex_free_waiter(&waiter);
}
/**
* __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop
* @lock: the rt_mutex to take
* @state: the state the task should block in (TASK_INTERRUPTIBLE
* or TASK_UNINTERRUPTIBLE)
* @timeout: the pre-initialized and started timer, or NULL for none
* @waiter: the pre-initialized rt_mutex_waiter
* @detect_deadlock: passed to task_blocks_on_rt_mutex
*
* lock->wait_lock must be held by the caller.
*/
static int __sched
__rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
struct rt_mutex_waiter *waiter,
int detect_deadlock)
{
int ret = 0;
for (;;) {
/* Try to acquire the lock: */
if (try_to_take_rt_mutex(lock))
break;
/*
* TASK_INTERRUPTIBLE checks for signals and
* timeout. Ignored otherwise.
*/
if (unlikely(state == TASK_INTERRUPTIBLE)) {
/* Signal pending? */
if (signal_pending(current))
ret = -EINTR;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
if (ret)
break;
}
/*
* waiter->task is NULL the first time we come here and
* when we have been woken up by the previous owner
* but the lock got stolen by a higher prio task.
*/
if (!waiter->task) {
ret = task_blocks_on_rt_mutex(lock, waiter, current,
detect_deadlock);
/*
* If we got woken up by the owner then start loop
* all over without going into schedule to try
* to get the lock now:
*/
if (unlikely(!waiter->task)) {
/*
* Reset the return value. We might
* have returned with -EDEADLK and the
* owner released the lock while we
* were walking the pi chain.
*/
ret = 0;
continue;
}
if (unlikely(ret))
break;
}
raw_spin_unlock(&lock->wait_lock);
debug_rt_mutex_print_deadlock(waiter);
if (waiter->task)
schedule_rt_mutex(lock);
raw_spin_lock(&lock->wait_lock);
set_current_state(state);
}
return ret;
}
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
int detect_deadlock)
{
int ret = 0, saved_lock_depth = -1;
struct rt_mutex_waiter waiter;
unsigned long flags;
debug_rt_mutex_init_waiter(&waiter);
raw_spin_lock_irqsave(&lock->wait_lock, flags);
init_lists(lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock, current, NULL)) {
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
return 0;
}
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout)) {
hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
if (!hrtimer_active(&timeout->timer))
timeout->task = NULL;
}
ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock, flags, 0);
/*
* We drop the BKL here before we go into the wait loop to avoid a
* possible deadlock in the scheduler.
*
* Note: This must be done after we call task_blocks_on_rt_mutex
* because rt_release_bkl() releases the wait_lock and will
* cause a race between setting the mark waiters flag in
* the owner field and adding this task to the wait list. Those
* two must be done within the protection of the wait_lock.
*/
if (unlikely(current->lock_depth >= 0))
saved_lock_depth = rt_release_bkl(lock, flags);
if (likely(!ret))
ret = __rt_mutex_slowlock(lock, state, timeout, &waiter, flags);
set_current_state(TASK_RUNNING);
if (unlikely(ret))
remove_waiter(lock, &waiter, flags);
BUG_ON(!plist_node_empty(&waiter.list_entry));
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
/* Must we reaquire the BKL? */
if (unlikely(saved_lock_depth >= 0))
rt_reacquire_bkl(saved_lock_depth);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}
/*
* Slow path lock function:
*/
static int __sched
rt_mutex_slowlock(struct rt_mutex *lock, int state,
struct hrtimer_sleeper *timeout,
int detect_deadlock)
{
struct rt_mutex_waiter waiter;
int ret = 0;
debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
spin_lock(&lock->wait_lock);
/* Try to acquire the lock again: */
if (try_to_take_rt_mutex(lock)) {
spin_unlock(&lock->wait_lock);
return 0;
}
set_current_state(state);
/* Setup the timer, when timeout != NULL */
if (unlikely(timeout))
hrtimer_start(&timeout->timer, timeout->timer.expires,
HRTIMER_MODE_ABS);
for (;;) {
/* Try to acquire the lock: */
if (try_to_take_rt_mutex(lock))
break;
/*
* TASK_INTERRUPTIBLE checks for signals and
* timeout. Ignored otherwise.
*/
if (unlikely(state == TASK_INTERRUPTIBLE)) {
/* Signal pending? */
if (signal_pending(current))
ret = -EINTR;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
if (ret)
break;
}
/*
* waiter.task is NULL the first time we come here and
* when we have been woken up by the previous owner
* but the lock got stolen by a higher prio task.
*/
if (!waiter.task) {
ret = task_blocks_on_rt_mutex(lock, &waiter,
detect_deadlock);
/*
* If we got woken up by the owner then start loop
* all over without going into schedule to try
* to get the lock now:
*/
if (unlikely(!waiter.task)) {
/*
* Reset the return value. We might
* have returned with -EDEADLK and the
* owner released the lock while we
* were walking the pi chain.
*/
ret = 0;
continue;
}
if (unlikely(ret))
break;
}
spin_unlock(&lock->wait_lock);
debug_rt_mutex_print_deadlock(&waiter);
if (waiter.task)
schedule_rt_mutex(lock);
spin_lock(&lock->wait_lock);
set_current_state(state);
}
set_current_state(TASK_RUNNING);
if (unlikely(waiter.task))
remove_waiter(lock, &waiter);
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up.
*/
fixup_rt_mutex_waiters(lock);
spin_unlock(&lock->wait_lock);
/* Remove pending timer: */
if (unlikely(timeout))
hrtimer_cancel(&timeout->timer);
/*
* Readjust priority, when we did not get the lock. We might
* have been the pending owner and boosted. Since we did not
* take the lock, the PI boost has to go.
*/
if (unlikely(ret))
rt_mutex_adjust_prio(current);
debug_rt_mutex_free_waiter(&waiter);
return ret;
}