From: Jason Gunthorpe <jgg@ziepe.ca>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org,
"DRI Development" <dri-devel@lists.freedesktop.org>,
"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Michal Hocko" <mhocko@suse.com>,
"Christian König" <christian.koenig@amd.com>,
"David Rientjes" <rientjes@google.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Daniel Vetter" <daniel.vetter@intel.com>
Subject: Re: [PATCH 1/5] mm: Check if mmu notifier callbacks are allowed to fail
Date: Fri, 16 Aug 2019 14:19:04 -0300 [thread overview]
Message-ID: <20190816171904.GA3166@ziepe.ca> (raw)
In-Reply-To: <20190814202027.18735-2-daniel.vetter@ffwll.ch>
On Wed, Aug 14, 2019 at 10:20:23PM +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.
>
> v5: Fixup rebase damage and also catch failures != EAGAIN for
> !blockable (Jason). Also go back to WARN_ON as requested by Jason, so
> automatic checkers can easily catch bugs by setting panic_on_warn.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Christian König" <christian.koenig@amd.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: linux-mm@kvack.org
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
> mm/mmu_notifier.c | 2 ++
> 1 file changed, 2 insertions(+)
Applied to hmm.git, thanks
Jason
next prev parent reply other threads:[~2019-08-16 17:19 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 20:20 [PATCH 0/5] hmm & mmu_notifier debug/lockdep annotations Daniel Vetter
2019-08-14 20:20 ` [PATCH 1/5] mm: Check if mmu notifier callbacks are allowed to fail Daniel Vetter
2019-08-14 22:14 ` Andrew Morton
2019-08-14 23:22 ` Jason Gunthorpe
2019-08-14 23:34 ` Ralph Campbell
2019-08-16 17:19 ` Jason Gunthorpe [this message]
2019-08-14 20:20 ` [PATCH 2/5] kernel.h: Add non_block_start/end() Daniel Vetter
2019-08-14 20:45 ` Andrew Morton
2019-08-15 6:52 ` Daniel Vetter
2019-08-15 8:44 ` Michal Hocko
2019-08-15 13:04 ` Jason Gunthorpe
2019-08-15 13:12 ` Daniel Vetter
2019-08-15 14:37 ` Jason Gunthorpe
2019-08-15 14:43 ` Daniel Vetter
2019-08-15 15:10 ` Jason Gunthorpe
2019-08-15 16:25 ` Daniel Vetter
2019-08-15 17:35 ` Jason Gunthorpe
2019-08-15 17:39 ` Jerome Glisse
2019-08-15 18:01 ` Jason Gunthorpe
2019-08-15 18:27 ` Jerome Glisse
2019-08-15 18:57 ` Jason Gunthorpe
2019-08-15 16:32 ` Jerome Glisse
2019-08-15 17:16 ` Jason Gunthorpe
2019-08-15 17:21 ` Daniel Vetter
2019-08-15 17:35 ` Jerome Glisse
2019-08-15 13:24 ` Michal Hocko
2019-08-15 22:15 ` Andrew Morton
2019-08-16 8:24 ` Michal Hocko
2019-08-14 23:58 ` Jason Gunthorpe
2019-08-15 6:58 ` Daniel Vetter
2019-08-15 12:23 ` Jason Gunthorpe
2019-08-15 13:21 ` Michal Hocko
2019-08-15 14:12 ` Jason Gunthorpe
2019-08-15 16:00 ` Michal Hocko
2019-08-15 16:56 ` Jason Gunthorpe
2019-08-15 17:11 ` Jerome Glisse
2019-08-15 17:17 ` Jason Gunthorpe
2019-08-15 17:42 ` Michal Hocko
2019-08-15 17:57 ` Jerome Glisse
2019-08-15 18:24 ` Jason Gunthorpe
2019-08-15 19:05 ` Michal Hocko
2019-08-15 19:18 ` Jason Gunthorpe
2019-08-15 19:35 ` Michal Hocko
2019-08-15 20:13 ` Jason Gunthorpe
2019-08-16 8:10 ` Michal Hocko
2019-08-16 12:19 ` Jason Gunthorpe
2019-08-16 12:26 ` Michal Hocko
2019-08-15 20:16 ` [Intel-gfx] " Daniel Vetter
2019-08-15 20:27 ` Jason Gunthorpe
2019-08-15 20:49 ` Daniel Vetter
2019-08-16 1:00 ` Jason Gunthorpe
2019-08-16 6:20 ` Daniel Vetter
2019-08-16 12:12 ` Jason Gunthorpe
2019-08-16 14:11 ` Daniel Vetter
2019-08-16 14:38 ` Jason Gunthorpe
2019-08-16 16:36 ` Daniel Vetter
2019-08-16 16:54 ` Jason Gunthorpe
2019-08-16 8:27 ` Michal Hocko
2019-08-14 20:20 ` [PATCH 3/5] mm, notifier: Catch sleeping/blocking for !blockable Daniel Vetter
2019-08-15 0:00 ` Jason Gunthorpe
2019-08-15 7:02 ` Daniel Vetter
[not found] ` <20190815123556.GB21596@ziepe.ca>
2019-08-17 16:09 ` Daniel Vetter
2019-08-14 20:20 ` [PATCH 4/5] mm, notifier: Add a lockdep map for invalidate_range_start Daniel Vetter
2019-08-15 0:09 ` Jason Gunthorpe
2019-08-15 7:10 ` Daniel Vetter
2019-08-15 12:53 ` Jason Gunthorpe
2019-08-14 20:20 ` [PATCH 5/5] mm/hmm: WARN on illegal ->sync_cpu_device_pagetables errors Daniel Vetter
2019-08-15 0:11 ` Jason Gunthorpe
2019-08-15 7:14 ` Daniel Vetter
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