On Fri, 2015-03-06 at 20:44 -0800, Davidlohr Bueso wrote: > On Fri, 2015-03-06 at 20:31 -0800, Jason Low wrote: > > On Fri, 2015-03-06 at 13:12 -0800, Jason Low wrote: > > > > Just in case, here's the updated patch which addresses Linus's comments > > and with a changelog. > > > > Note: The changelog says that it fixes (locking/rwsem: Avoid deceiving > > lock spinners), though I still haven't seen full confirmation that it > > addresses all of the lockup reports. > > > > ------ > > Subject: [PATCH] rwsem: Avoid spinning when owner is not running > > > > Fixes tip commmit b3fd4f03ca0b (locking/rwsem: Avoid deceiving lock > > spinners). > > > > 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. > > I would mention the actual effects of the bug, either just a "lockup" > and/or a fragment of the trace.
Right, we should mention about the lockup in the changelog. > > Cc: Ming Lei <ming....@canonical.com> > > Cc: Davidlohr Bueso <d...@stgolabs.net> > > Acked-by: Davidlohr Bueso <d...@stgolabs.net> Thanks! -- 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/
