pthread_cond_wait() should be an atomic operation in the mutex lock/unlock.
Since the sched_lock() has been wrongly deleted in the previous commit,
the context switch will occurred after the mutex was unlocked:
--------------------------------------------------------------------
Task1(Priority 100) | Task2(Priority 101)
|
pthread_mutex_lock(mutex); |
| |
pthread_cond_wait(cond, mutex) |
| | |
| | |
| ->enter_critical_section() |
| ->pthread_mutex_give(mutex) | ----> pthread_mutex_lock(mutex); // contex switch to high priority task
| | pthread_cond_signal(cond); // signal before wait
| | <---- pthread_mutex_unlock(mutex); // switch back to original task
| ->pthread_sem_take(cond->sem)| // try to wait the signal, Deadlock.
| ->leave_critical_section() |
|
| ->pthread_mutex_take(mutex) |
| |
pthread_mutex_lock(mutex); |
---------------------------------------------------------------------
This PR will bring back sched_lock()/sched_unlock() to avoid context switch to ensure atomicity
Signed-off-by: chao an <anchao@xiaomi.com>
b9b615b425