On Tue, May 21, 2019 at 11:44:11AM -0400, Jerome Glisse wrote: > On Mon, May 20, 2019 at 11:39:42PM +0200, Daniel Vetter wrote: > > Just a bit of paranoia, since if we start pushing this deep into > > callchains it's hard to spot all places where an mmu notifier > > implementation might fail when it's not allowed to. > > > > Inspired by some confusion we had discussing i915 mmu notifiers and > > whether we could use the newly-introduced return value to handle some > > corner cases. Until we realized that these are only for when a task > > has been killed by the oom reaper. > > > > An alternative approach would be to split the callback into two > > versions, one with the int return value, and the other with void > > return value like in older kernels. But that's a lot more churn for > > fairly little gain I think. > > > > Summary from the m-l discussion on why we want something at warning > > level: This allows automated tooling in CI to catch bugs without > > humans having to look at everything. If we just upgrade the existing > > pr_info to a pr_warn, then we'll have false positives. And as-is, no > > one will ever spot the problem since it's lost in the massive amounts > > of overall dmesg noise. > > > > v2: Drop the full WARN_ON backtrace in favour of just a pr_warn for > > the problematic case (Michal Hocko). > > > > v3: Rebase on top of Glisse's arg rework. > > > > v4: More rebase on top of Glisse reworking everything. > > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Michal Hocko <mhocko@xxxxxxxx> > > Cc: "Christian König" <christian.koenig@xxxxxxx> > > Cc: David Rientjes <rientjes@xxxxxxxxxx> > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> > > Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx> > > Cc: linux-mm@xxxxxxxxx > > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > Reviewed-by: Christian König <christian.koenig@xxxxxxx> > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx> -mm folks, is this (entire series of 4 patches) planned to land in the 5.3 merge window? Or do you want more reviews/testing/polish? I think with all the hmm rework going on, a bit more validation and checks in this tricky area would help. Thanks, Daniel > > > --- > > mm/mmu_notifier.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c > > index ee36068077b6..c05e406a7cd7 100644 > > --- a/mm/mmu_notifier.c > > +++ b/mm/mmu_notifier.c > > @@ -181,6 +181,9 @@ int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) > > pr_info("%pS callback failed with %d in %sblockable context.\n", > > mn->ops->invalidate_range_start, _ret, > > !mmu_notifier_range_blockable(range) ? "non-" : ""); > > + if (!mmu_notifier_range_blockable(range)) > > + pr_warn("%pS callback failure not allowed\n", > > + mn->ops->invalidate_range_start); > > ret = _ret; > > } > > } > > -- > > 2.20.1 > > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch