Re: safety of *mutex_unlock() (Was: [BUG] signal: sighand unprotected when accessed by /proc)

Oleg Nesterov
2014-06-18T16:45:31Z

On 06/17, Paul E. McKenney wrote:
>
> + if (drop_boost_mutex) {
> + rt_mutex_unlock(&rnp->boost_mtx);
> complete(&rnp->boost_completion);

Well, I still do not understand this ->boost_completion...

> - /* Wait until boostee is done accessing mtx before reinitializing. */
> + /* Wait for boostee to be done w/boost_mtx before reinitializing. */
> wait_for_completion(&rnp->boost_completion);

OK, at least we have a comment.

But let me repeat. Thomas has already fixed rt_mutex, unlock is atomic.
It doesn't touch this memory after it makes another lock() possible.

And (contrary to what I said initially) we can rely on this because -rt
converts spinlock_t into rt_mutex ?

Oleg.