From: Qian Cai <cai@lca.pw>
To: "Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
"DRI Development" <dri-devel@lists.freedesktop.org>,
LKML <linux-kernel@vger.kernel.org>,
"amd-gfx list" <amd-gfx@lists.freedesktop.org>,
"Thomas Hellström" <thomas_os@shipmail.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Linux MM" <linux-mm@kvack.org>,
linux-rdma <linux-rdma@vger.kernel.org>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Christian König" <christian.koenig@amd.com>,
"Daniel Vetter" <daniel.vetter@intel.com>,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH] mm: Track mmu notifiers in fs_reclaim_acquire/release
Date: Sun, 21 Jun 2020 18:09:37 -0400 [thread overview]
Message-ID: <20200621220937.GA2034@lca.pw> (raw)
In-Reply-To: <20200621200103.GV20149@phenom.ffwll.local>
On Sun, Jun 21, 2020 at 10:01:03PM +0200, Daniel Vetter wrote:
> On Sun, Jun 21, 2020 at 08:07:08PM +0200, Daniel Vetter wrote:
> > On Sun, Jun 21, 2020 at 7:42 PM Qian Cai <cai@lca.pw> wrote:
> > >
> > > On Wed, Jun 10, 2020 at 09:41:01PM +0200, Daniel Vetter wrote:
> > > > fs_reclaim_acquire/release nicely catch recursion issues when
> > > > allocating GFP_KERNEL memory against shrinkers (which gpu drivers tend
> > > > to use to keep the excessive caches in check). For mmu notifier
> > > > recursions we do have lockdep annotations since 23b68395c7c7
> > > > ("mm/mmu_notifiers: add a lockdep map for invalidate_range_start/end").
> > > >
> > > > But these only fire if a path actually results in some pte
> > > > invalidation - for most small allocations that's very rarely the case.
> > > > The other trouble is that pte invalidation can happen any time when
> > > > __GFP_RECLAIM is set. Which means only really GFP_ATOMIC is a safe
> > > > choice, GFP_NOIO isn't good enough to avoid potential mmu notifier
> > > > recursion.
> > > >
> > > > I was pondering whether we should just do the general annotation, but
> > > > there's always the risk for false positives. Plus I'm assuming that
> > > > the core fs and io code is a lot better reviewed and tested than
> > > > random mmu notifier code in drivers. Hence why I decide to only
> > > > annotate for that specific case.
> > > >
> > > > Furthermore even if we'd create a lockdep map for direct reclaim, we'd
> > > > still need to explicit pull in the mmu notifier map - there's a lot
> > > > more places that do pte invalidation than just direct reclaim, these
> > > > two contexts arent the same.
> > > >
> > > > Note that the mmu notifiers needing their own independent lockdep map
> > > > is also the reason we can't hold them from fs_reclaim_acquire to
> > > > fs_reclaim_release - it would nest with the acquistion in the pte
> > > > invalidation code, causing a lockdep splat. And we can't remove the
> > > > annotations from pte invalidation and all the other places since
> > > > they're called from many other places than page reclaim. Hence we can
> > > > only do the equivalent of might_lock, but on the raw lockdep map.
> > > >
> > > > With this we can also remove the lockdep priming added in 66204f1d2d1b
> > > > ("mm/mmu_notifiers: prime lockdep") since the new annotations are
> > > > strictly more powerful.
> > > >
> > > > v2: Review from Thomas Hellstrom:
> > > > - unbotch the fs_reclaim context check, I accidentally inverted it,
> > > > but it didn't blow up because I inverted it immediately
> > > > - fix compiling for !CONFIG_MMU_NOTIFIER
> > > >
> > > > Cc: Thomas Hellström (Intel) <thomas_os@shipmail.org>
> > > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > > Cc: Jason Gunthorpe <jgg@mellanox.com>
> > > > Cc: linux-mm@kvack.org
> > > > Cc: linux-rdma@vger.kernel.org
> > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > Cc: Christian König <christian.koenig@amd.com>
> > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > >
> > > Replying the right patch here...
> > >
> > > Reverting this commit [1] fixed the lockdep warning below while applying
> > > some memory pressure.
> > >
> > > [1] linux-next cbf7c9d86d75 ("mm: track mmu notifiers in fs_reclaim_acquire/release")
> >
> > Hm, then I'm confused because
> > - there's not mmut notifier lockdep map in the splat at a..
> > - the patch is supposed to not change anything for fs_reclaim (but the
> > interim version got that wrong)
> > - looking at the paths it's kmalloc vs kswapd, both places I totally
> > expect fs_reflaim to be used.
> >
> > But you're claiming reverting this prevents the lockdep splat. If
> > that's right, then my reasoning above is broken somewhere. Someone
> > less blind than me having an idea?
> >
> > Aside this is the first email I've typed, until I realized the first
> > report was against the broken patch and that looked like a much more
> > reasonable explanation (but didn't quite match up with the code
> > paths).
>
> Below diff should undo the functional change in my patch. Can you pls test
> whether the lockdep splat is really gone with that? Might need a lot of
> testing and memory pressure to be sure, since all these reclaim paths
> aren't very deterministic.
Well, I am running even heavy memory pressure workloads on linux-next
like every day, and never saw this splat until today where your patch
first show up.
Since I am rather busy tracking another regression, here is the steps to
reproduce (super easy to reproduce on multiple machines here.):
# git clone https://github.com/cailca/linux-mm.git
# cd linux-mm; make
# ./random 0
The .config is in there as well if ever matters.
next prev parent reply other threads:[~2020-06-21 22:09 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 8:12 [PATCH 00/18] dma-fence lockdep annotations, round 2 Daniel Vetter
2020-06-04 8:12 ` [PATCH 01/18] mm: Track mmu notifiers in fs_reclaim_acquire/release Daniel Vetter
2020-06-10 12:01 ` Thomas Hellström (Intel)
2020-06-10 12:25 ` [Intel-gfx] " Daniel Vetter
2020-06-10 19:41 ` [PATCH] " Daniel Vetter
2020-06-11 14:29 ` Jason Gunthorpe
2020-06-21 17:42 ` Qian Cai
2020-06-21 18:07 ` Daniel Vetter
2020-06-21 20:01 ` Daniel Vetter
2020-06-21 22:09 ` Qian Cai [this message]
2020-06-23 16:17 ` Qian Cai
2020-06-23 22:13 ` Daniel Vetter
2020-06-23 22:29 ` Qian Cai
2020-06-23 22:31 ` Dave Chinner
2020-06-23 22:36 ` Daniel Vetter
2020-06-21 17:00 ` [PATCH 01/18] " Qian Cai
2020-06-21 17:28 ` Daniel Vetter
2020-06-21 17:46 ` Qian Cai
2020-06-04 8:12 ` [PATCH 02/18] dma-buf: minor doc touch-ups Daniel Vetter
2020-06-10 13:07 ` Thomas Hellström (Intel)
2020-06-04 8:12 ` [PATCH 03/18] dma-fence: basic lockdep annotations Daniel Vetter
2020-06-04 8:57 ` Thomas Hellström (Intel)
2020-06-04 9:21 ` Daniel Vetter
[not found] ` <159126281827.25109.3992161193069793005@build.alporthouse.com>
2020-06-04 9:36 ` [Intel-gfx] " Daniel Vetter
2020-06-05 13:29 ` [PATCH] " Daniel Vetter
2020-06-05 14:30 ` Thomas Hellström (Intel)
2020-06-11 9:57 ` Maarten Lankhorst
2020-06-10 14:21 ` [Intel-gfx] [PATCH 03/18] " Tvrtko Ursulin
2020-06-10 15:17 ` Daniel Vetter
2020-06-11 10:36 ` Tvrtko Ursulin
2020-06-11 11:29 ` Daniel Vetter
2020-06-11 14:29 ` Tvrtko Ursulin
2020-06-11 15:03 ` Daniel Vetter
[not found] ` <159186243606.1506.4437341616828968890@build.alporthouse.com>
2020-06-11 8:44 ` Dave Airlie
2020-06-11 9:01 ` [Intel-gfx] " Daniel Stone
[not found] ` <159255511144.7737.12635440776531222029@build.alporthouse.com>
2020-06-19 8:51 ` Daniel Vetter
[not found] ` <159255801588.7737.4425728073225310839@build.alporthouse.com>
2020-06-19 9:43 ` Daniel Vetter
[not found] ` <159257233754.7737.17318605310513355800@build.alporthouse.com>
2020-06-22 9:16 ` Daniel Vetter
2020-07-09 7:29 ` Daniel Stone
2020-07-09 8:01 ` Daniel Vetter
2020-06-12 7:06 ` [PATCH] " Daniel Vetter
2020-06-04 8:12 ` [PATCH 04/18] dma-fence: prime " Daniel Vetter
2020-06-11 7:30 ` [Linaro-mm-sig] " Thomas Hellström (Intel)
2020-06-11 8:34 ` Daniel Vetter
2020-06-11 14:15 ` Jason Gunthorpe
2020-06-11 23:35 ` Felix Kuehling
2020-06-12 5:11 ` Daniel Vetter
2020-06-19 18:13 ` Jerome Glisse
2020-06-23 7:39 ` Daniel Vetter
2020-06-23 18:44 ` Felix Kuehling
2020-06-23 19:02 ` Daniel Vetter
2020-06-16 12:07 ` Daniel Vetter
2020-06-16 14:53 ` Jason Gunthorpe
2020-06-17 7:57 ` Daniel Vetter
2020-06-17 15:29 ` Jason Gunthorpe
2020-06-18 14:42 ` Daniel Vetter
2020-06-17 6:48 ` Daniel Vetter
2020-06-17 15:28 ` Jason Gunthorpe
2020-06-18 15:00 ` Daniel Vetter
2020-06-18 17:23 ` Jason Gunthorpe
2020-06-19 7:22 ` Daniel Vetter
2020-06-19 11:39 ` Jason Gunthorpe
2020-06-19 15:06 ` Daniel Vetter
2020-06-19 15:15 ` Jason Gunthorpe
2020-06-19 16:19 ` Daniel Vetter
2020-06-19 17:23 ` Jason Gunthorpe
2020-06-19 18:09 ` Jerome Glisse
2020-06-19 18:18 ` Jason Gunthorpe
2020-06-19 19:48 ` Felix Kuehling
2020-06-19 19:55 ` Jason Gunthorpe
2020-06-19 20:03 ` Felix Kuehling
2020-06-19 20:31 ` Jerome Glisse
2020-06-22 11:46 ` Jason Gunthorpe
2020-06-22 20:15 ` Jerome Glisse
2020-06-23 0:02 ` Jason Gunthorpe
2020-06-19 20:10 ` Jerome Glisse
2020-06-19 20:43 ` Daniel Vetter
2020-06-19 20:59 ` Jerome Glisse
2020-06-23 0:05 ` Jason Gunthorpe
2020-06-19 19:11 ` Alex Deucher
2020-06-19 19:30 ` Felix Kuehling
2020-06-19 19:40 ` Jerome Glisse
2020-06-19 19:51 ` Jason Gunthorpe
2020-06-12 7:01 ` [PATCH] " Daniel Vetter
2020-06-04 8:12 ` [PATCH 05/18] drm/vkms: Annotate vblank timer Daniel Vetter
2020-06-04 8:12 ` [PATCH 06/18] drm/vblank: Annotate with dma-fence signalling section Daniel Vetter
2020-06-04 8:12 ` [PATCH 07/18] drm/atomic-helper: Add dma-fence annotations Daniel Vetter
2020-06-04 8:12 ` [PATCH 08/18] drm/amdgpu: add dma-fence annotations to atomic commit path Daniel Vetter
2020-06-23 10:51 ` Daniel Vetter
2020-06-04 8:12 ` [PATCH 09/18] drm/scheduler: use dma-fence annotations in main thread Daniel Vetter
2020-06-04 8:12 ` [PATCH 10/18] drm/amdgpu: use dma-fence annotations in cs_submit() Daniel Vetter
2020-06-04 8:12 ` [PATCH 11/18] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code Daniel Vetter
2020-06-04 8:12 ` [PATCH 12/18] drm/amdgpu: DC also loves to allocate stuff where it shouldn't Daniel Vetter
2020-06-04 8:12 ` [PATCH 13/18] drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail Daniel Vetter
2020-06-05 8:30 ` Pierre-Eric Pelloux-Prayer
2020-06-05 12:41 ` Daniel Vetter
2020-06-04 8:12 ` [PATCH 14/18] drm/scheduler: use dma-fence annotations in tdr work Daniel Vetter
2020-06-04 8:12 ` [PATCH 15/18] drm/amdgpu: use dma-fence annotations for gpu reset code Daniel Vetter
2020-06-04 8:12 ` [PATCH 16/18] Revert "drm/amdgpu: add fbdev suspend/resume on gpu reset" Daniel Vetter
2020-06-04 8:12 ` [PATCH 17/18] drm/amdgpu: gpu recovery does full modesets Daniel Vetter
2020-06-04 8:12 ` [PATCH 18/18] drm/i915: Annotate dma_fence_work Daniel Vetter
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