From: Daniel Vetter <daniel@ffwll.ch>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: LKML <linux-kernel@vger.kernel.org>,
"Linux MM" <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>,
"David Rientjes" <rientjes@google.com>,
"Christian König" <christian.koenig@amd.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Daniel Vetter" <daniel.vetter@intel.com>
Subject: Re: [PATCH 3/5] mm, notifier: Catch sleeping/blocking for !blockable
Date: Sat, 17 Aug 2019 18:09:54 +0200 [thread overview]
Message-ID: <CAKMK7uFz1ZiUUK5+tGpf-9Gksu5uN72sFW_KpJ53BuSfKY8PVg@mail.gmail.com> (raw)
In-Reply-To: <20190815123556.GB21596@ziepe.ca>
On Sat, Aug 17, 2019 at 5:26 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Thu, Aug 15, 2019 at 09:02:49AM +0200, Daniel Vetter wrote:
> > On Wed, Aug 14, 2019 at 09:00:29PM -0300, Jason Gunthorpe wrote:
> > > On Wed, Aug 14, 2019 at 10:20:25PM +0200, Daniel Vetter wrote:
> > > > We need to make sure implementations don't cheat and don't have a
> > > > possible schedule/blocking point deeply burried where review can't
> > > > catch it.
> > > >
> > > > I'm not sure whether this is the best way to make sure all the
> > > > might_sleep() callsites trigger, and it's a bit ugly in the code flow.
> > > > But it gets the job done.
> > > >
> > > > Inspired by an i915 patch series which did exactly that, because the
> > > > rules haven't been entirely clear to us.
> > >
> > > I thought lockdep already was able to detect:
> > >
> > > spin_lock()
> > > might_sleep();
> > > spin_unlock()
> > >
> > > Am I mistaken? If yes, couldn't this patch just inject a dummy lockdep
> > > spinlock?
> >
> > Hm ... assuming I didn't get lost in the maze I think might_sleep (well
> > ___might_sleep) doesn't do any lockdep checking at all. And we want
> > might_sleep, since that catches a lot more than lockdep.
>
> Don't know how it works, but it sure looks like it does:
>
> This:
> spin_lock(&file->uobjects_lock);
> down_read(&file->hw_destroy_rwsem);
> up_read(&file->hw_destroy_rwsem);
> spin_unlock(&file->uobjects_lock);
>
> Causes:
>
> [ 33.324729] BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1444
> [ 33.325599] in_atomic(): 1, irqs_disabled(): 0, pid: 247, name: ibv_devinfo
> [ 33.326115] 3 locks held by ibv_devinfo/247:
> [ 33.326556] #0: 000000009edf8379 (&uverbs_dev->disassociate_srcu){....}, at: ib_uverbs_open+0xff/0x5f0 [ib_uverbs]
> [ 33.327657] #1: 000000005e0eddf1 (&uverbs_dev->lists_mutex){+.+.}, at: ib_uverbs_open+0x16c/0x5f0 [ib_uverbs]
> [ 33.328682] #2: 00000000505f509e (&(&file->uobjects_lock)->rlock){+.+.}, at: ib_uverbs_open+0x31a/0x5f0 [ib_uverbs]
>
> And this:
>
> spin_lock(&file->uobjects_lock);
> might_sleep();
> spin_unlock(&file->uobjects_lock);
>
> Causes:
>
> [ 16.867211] BUG: sleeping function called from invalid context at drivers/infiniband/core/uverbs_main.c:1095
> [ 16.867776] in_atomic(): 1, irqs_disabled(): 0, pid: 245, name: ibv_devinfo
> [ 16.868098] 3 locks held by ibv_devinfo/245:
> [ 16.868383] #0: 000000004c5954ff (&uverbs_dev->disassociate_srcu){....}, at: ib_uverbs_open+0xf8/0x600 [ib_uverbs]
> [ 16.868938] #1: 0000000020a6fae2 (&uverbs_dev->lists_mutex){+.+.}, at: ib_uverbs_open+0x16c/0x600 [ib_uverbs]
> [ 16.869568] #2: 00000000036e6a97 (&(&file->uobjects_lock)->rlock){+.+.}, at: ib_uverbs_open+0x317/0x600 [ib_uverbs]
>
> I think this is done in some very expensive way, so it probably only
> works when lockdep is enabled..
This is the might_sleep debug infrastructure (both of them), not
lockdep. Disable CONFIG_PROVE_LOCKING and you should still get these.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
next prev parent reply other threads:[~2019-08-17 16:10 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
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 [this message]
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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