On 03/07/2015 02:45 AM, Jason Low wrote: > Fixes tip commit b3fd4f03ca0b (locking/rwsem: Avoid deceiving lock spinners). > > Ming reported soft lockups occurring when running xfstest due to > commit b3fd4f03ca0b. > > When doing optimistic spinning in rwsem, threads should stop spinning when > the lock owner is not running. While a thread is spinning on owner, if > the owner reschedules, owner->on_cpu returns false and we stop spinning. > > However, commit b3fd4f03ca0b essentially caused the check to get ignored > because when we break out of the spin loop due to !on_cpu, we continue > spinning if sem->owner != NULL. > > This patch fixes this by making sure we stop spinning if the owner is not > running. Furthermore, just like with mutexes, refactor the code such that > we don't have separate checks for owner_running(). This makes it more > straightforward in terms of why we exit the spin on owner loop and we > would also avoid needing to "guess" why we broke out of the loop to make > this more readable.
That seems to solve the hangs I'm seeing as well. Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
