bartoszek/zephyr
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

kernel: mutex: fix races when lock timeout

Browse Source 
Say threadA holds a mutex and threadB tries
to lock it with a timeout, a race would occur
if threadA unlock that mutex after threadB
got unpended by sys_clock and before it gets
scheduled and calls k_spin_lock.

This patch fixes this issue by checking the
mutex's status again after k_spin_lock calls.

Fixes #48056

Signed-off-by: Qi Yang <qi.yang@cmind-semi.com>
This commit is contained in:
Qi Yang 2022-08-12 10:44:38 +08:00 committed by Carles Cufí
parent f28a8d2240
commit 89c4a074dc
1 changed files with 12 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
kernel/mutex.c
View File

@ -161,15 +161,21 @@ int z_impl_k_mutex_lock(struct k_mutex *mutex, k_timeout_t timeout)
key = k_spin_lock(&lock);
struct k_thread *waiter = z_waitq_head(&mutex->wait_q);
/*
* Check if mutex was unlocked after this thread was unpended.
* If so, skip adjusting owner's priority down.
*/
if (likely(mutex->owner != NULL)) {
struct k_thread *waiter = z_waitq_head(&mutex->wait_q);
new_prio = (waiter != NULL) ?
new_prio_for_inheritance(waiter->base.prio, mutex->owner_orig_prio) :
mutex->owner_orig_prio;
new_prio = (waiter != NULL) ?
new_prio_for_inheritance(waiter->base.prio, mutex->owner_orig_prio) :
mutex->owner_orig_prio;
LOG_DBG("adjusting prio down on mutex %p", mutex);
LOG_DBG("adjusting prio down on mutex %p", mutex);
resched = adjust_owner_prio(mutex, new_prio) || resched;
resched = adjust_owner_prio(mutex, new_prio) || resched;
}
if (resched) {
z_reschedule(&lock, key);