On Tue, 3 Nov 2020 12:08:47 +0100 Daniel Vetter <dan...@ffwll.ch> wrote:
> On Tue, Nov 03, 2020 at 12:03:26PM +0100, Boris Brezillon wrote: > > On Tue, 3 Nov 2020 11:25:40 +0100 > > Daniel Vetter <dan...@ffwll.ch> wrote: > > > > > On Tue, Nov 03, 2020 at 09:13:47AM +0100, Boris Brezillon wrote: > > > > We've fixed many races in panfrost_job_timedout() but some remain. > > > > Instead of trying to fix it again, let's simplify the logic and move > > > > the reset bits to a separate work scheduled when one of the queue > > > > reports a timeout. > > > > > > > > v3: > > > > - Replace the atomic_cmpxchg() by an atomic_xchg() (Robin Murphy) > > > > - Add Steven's R-b > > > > > > > > v2: > > > > - Use atomic_cmpxchg() to conditionally schedule the reset work (Steven > > > > Price) > > > > > > > > Fixes: 1a11a88cfd9a ("drm/panfrost: Fix job timeout handling") > > > > Cc: <sta...@vger.kernel.org> > > > > Signed-off-by: Boris Brezillon <boris.brezil...@collabora.com> > > > > Reviewed-by: Steven Price <steven.pr...@arm.com> > > > > > > Sprinkling the dma_fence annotations over this would be really nice ... > > > > You mean something like that? > > That's just the irq annotations, i.e. the one that's already guaranteed by > the irq vs. locks checks. So this does nothing. > > What I mean is annotating your new reset work (it's part of the critical > path to complete batches, since it's holding up other batches that are > stuck in the scheduler still), and the drm/scheduler annotations I've > floated a while ago. The drm/scheduler annotations are stuck somewhat for > lack of feedback from any of the driver teams using it though :-/ > > The thing is pulling something out into a worker of it's own generally > doesn't fix any deadlocks, it just hides them from lockdep. Hm, except that's not exactly a deadlock we were trying to fix here (as in, not a situation where 2 threads try to acquire locks in different orders), just a situation where the scheduler stops dequeuing jobs because it ends up in an inconsistent state (which is caused by a bad/lack-of synchronization between timeout handlers). The problem here is that we have 3 schedulers (one per HW queue) but when a timeout occurs on one of them, we need to reset them all, thus requiring some synchronization between the different timeout works. Moving the reset logic to a separate work simplifies the synchronization. > So it would be > good to make sure lockdep can see through your maze again. Okay, but it's not clear to me which part of the panfrost_reset() function should be annotated. I mean, I probably call functions that can signal fences, but I don't call dma_signal_fence() directly. Are callers of the dma_sched_xxx() helpers expected to place such annotations? _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel