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Fix missed rtmutex wakeups causing sporadic boot hangs

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and other misbehavior.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'locking-urgent-2024-12-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fix from Ingo Molnar:
 "Fix missed rtmutex wakeups causing sporadic boot hangs and other
  misbehavior"

* tag 'locking-urgent-2024-12-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rtmutex: Make sure we wake anything on the wake_q when we release the lock->wait_lock
This commit is contained in:
Linus Torvalds 2024-12-29 10:04:47 -08:00
commit bf7a281b80
2 changed files with 17 additions and 3 deletions
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18
kernel/locking/rtmutex.c
View File

@ -1292,7 +1292,13 @@ static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock,
*/
get_task_struct(owner);
preempt_disable();
raw_spin_unlock_irq(&lock->wait_lock);
/* wake up any tasks on the wake_q before calling rt_mutex_adjust_prio_chain */
wake_up_q(wake_q);
wake_q_init(wake_q);
preempt_enable();
res = rt_mutex_adjust_prio_chain(owner, chwalk, lock,
next_lock, waiter, task);
@ -1596,6 +1602,7 @@ static void __sched remove_waiter(struct rt_mutex_base *lock,
* or TASK_UNINTERRUPTIBLE)
* @timeout: the pre-initialized and started timer, or NULL for none
* @waiter: the pre-initialized rt_mutex_waiter
* @wake_q: wake_q of tasks to wake when we drop the lock->wait_lock
*
* Must be called with lock->wait_lock held and interrupts disabled
*/
@ -1603,7 +1610,8 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
struct ww_acquire_ctx *ww_ctx,
unsigned int state,
struct hrtimer_sleeper *timeout,
struct rt_mutex_waiter *waiter)
struct rt_mutex_waiter *waiter,
struct wake_q_head *wake_q)
__releases(&lock->wait_lock) __acquires(&lock->wait_lock)
{
struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex);
@ -1634,7 +1642,13 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
owner = rt_mutex_owner(lock);
else
owner = NULL;
preempt_disable();
raw_spin_unlock_irq(&lock->wait_lock);
if (wake_q) {
wake_up_q(wake_q);
wake_q_init(wake_q);
}
preempt_enable();
if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner))
rt_mutex_schedule();
@ -1708,7 +1722,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
ret = task_blocks_on_rt_mutex(lock, waiter, current, ww_ctx, chwalk, wake_q);
if (likely(!ret))
ret = rt_mutex_slowlock_block(lock, ww_ctx, state, NULL, waiter);
ret = rt_mutex_slowlock_block(lock, ww_ctx, state, NULL, waiter, wake_q);
if (likely(!ret)) {
/* acquired the lock */

2
kernel/locking/rtmutex_api.c
View File

@ -383,7 +383,7 @@ int __sched rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
raw_spin_lock_irq(&lock->wait_lock);
/* sleep on the mutex */
set_current_state(TASK_INTERRUPTIBLE);
ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter);
ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter, NULL);
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.