Re: [PATCH] Fix data race in mark_rt_mutex_waiters

On 1/20/2023 5:55 AM, Hernan Ponce de Leon wrote:

From: Hernan Ponce de Leon hernanl.leon@huawei.com

kernel/locking/rtmutex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 010cf4e6d0b8..7ed9472edd48 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -235,7 +235,7 @@ static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock) unsigned long owner, *p = (unsigned long *) &lock->owner; do {

• owner = *p;
  

• owner = READ_ONCE(*p);
  

  } while (cmpxchg_relaxed(p, owner,

I don't see how this makes any difference at all. *p can be read a dozen times and it's fine; cmpxchg has barrier semantics for compilers afaics