On 1/26/23 17:10, David Laight wrote:
From: Hernan Ponce de Leon
Sent: 26 January 2023 21:07
...
static __always_inline void rt_mutex_clear_owner(struct rt_mutex_base *lock) @@ -232,12 +232,7 @@ static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock, */ static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock) {
- unsigned long owner, *p = (unsigned long *) &lock->owner;
- do {
owner = *p;- } while (cmpxchg_relaxed(p, owner,
owner | RT_MUTEX_HAS_WAITERS) != owner);
- atomic_long_or(RT_MUTEX_HAS_WAITERS, (atomic_long_t *)&lock->owner);
These *(int_type *)&foo accesses (quite often just plain wrong) made me look up the definitions.
All one big accident waiting to happen... RT_MUTEX_HAS_WAITERS is defined in a different header to the structure. The explanatory comment is in a 3rd file.
It would all be safer if lock->owner were atomic_long_t with a comment that it was the waiting task_struct | RT_MUTEX_HAS_WAITERS.
Given the actual definition is rt_mutex_base_is_locked() even correct?
It is arguable if it should be considered locked if a waiter is waiting but the lock is at an unlock state at the moment. Mutex has a narrower definition of locked while others have a broader one.
Cheers, Longman