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From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: "Thomas Hellström (Intel)" <thomas_os@shipmail.org>
Cc: linux-rdma <linux-rdma@vger.kernel.org>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"amd-gfx list" <amd-gfx@lists.freedesktop.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Jason Gunthorpe" <jgg@mellanox.com>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [Intel-gfx] [PATCH 01/18] mm: Track mmu notifiers in fs_reclaim_acquire/release
Date: Wed, 10 Jun 2020 14:25:59 +0200
Message-ID: <CAKMK7uGF_ghH-3hT5QMKHuzToP50xj3OaDzAtdjO-d8H9svdjQ@mail.gmail.com> (raw)
In-Reply-To: <15bcdddd-b560-e98b-eaec-62277b5ab4af@shipmail.org>

On Wed, Jun 10, 2020 at 2:01 PM Thomas Hellström (Intel)
<thomas_os@shipmail.org> wrote:
>
> Hi, Daniel,
>
> Please see below.
>
> On 6/4/20 10:12 AM, 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.
> >
> > 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>
> > ---
> > This is part of a gpu lockdep annotation series simply because it
> > really helps to catch issues where gpu subsystem locks and primitives
> > can deadlock with themselves through allocations and mmu notifiers.
> > But aside from that motivation it should be completely free-standing,
> > and can land through -mm/-rdma/-hmm or any other tree really whenever.
> > -Daniel
> > ---
> >   mm/mmu_notifier.c |  7 -------
> >   mm/page_alloc.c   | 23 ++++++++++++++---------
> >   2 files changed, 14 insertions(+), 16 deletions(-)
> >
> > diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> > index 06852b896fa6..5d578b9122f8 100644
> > --- a/mm/mmu_notifier.c
> > +++ b/mm/mmu_notifier.c
> > @@ -612,13 +612,6 @@ int __mmu_notifier_register(struct mmu_notifier *subscription,
> >       lockdep_assert_held_write(&mm->mmap_sem);
> >       BUG_ON(atomic_read(&mm->mm_users) <= 0);
> >
> > -     if (IS_ENABLED(CONFIG_LOCKDEP)) {
> > -             fs_reclaim_acquire(GFP_KERNEL);
> > -             lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
> > -             lock_map_release(&__mmu_notifier_invalidate_range_start_map);
> > -             fs_reclaim_release(GFP_KERNEL);
> > -     }
> > -
> >       if (!mm->notifier_subscriptions) {
> >               /*
> >                * kmalloc cannot be called under mm_take_all_locks(), but we
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 13cc653122b7..f8a222db4a53 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -57,6 +57,7 @@
> >   #include <trace/events/oom.h>
> >   #include <linux/prefetch.h>
> >   #include <linux/mm_inline.h>
> > +#include <linux/mmu_notifier.h>
> >   #include <linux/migrate.h>
> >   #include <linux/hugetlb.h>
> >   #include <linux/sched/rt.h>
> > @@ -4124,7 +4125,7 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
> >   static struct lockdep_map __fs_reclaim_map =
> >       STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
> >
> > -static bool __need_fs_reclaim(gfp_t gfp_mask)
> > +static bool __need_reclaim(gfp_t gfp_mask)
> >   {
> >       gfp_mask = current_gfp_context(gfp_mask);
> >
> > @@ -4136,10 +4137,6 @@ static bool __need_fs_reclaim(gfp_t gfp_mask)
> >       if (current->flags & PF_MEMALLOC)
> >               return false;
> >
> > -     /* We're only interested __GFP_FS allocations for now */
> > -     if (!(gfp_mask & __GFP_FS))
> > -             return false;
> > -
> >       if (gfp_mask & __GFP_NOLOCKDEP)
> >               return false;
> >
> > @@ -4158,15 +4155,23 @@ void __fs_reclaim_release(void)
> >
> >   void fs_reclaim_acquire(gfp_t gfp_mask)
> >   {
> > -     if (__need_fs_reclaim(gfp_mask))
> > -             __fs_reclaim_acquire();
> > +     if (__need_reclaim(gfp_mask)) {
> > +             if (!(gfp_mask & __GFP_FS))
> Hmm. Shouldn't this be "if (gfp_mask & __GFP_FS)" or am I misunderstanding?

Uh yes :-( I guess what saved me is that I immediately went for the
lockdep splat in drivers/gpu. And I guess there's not any obvious
inversions for GFP_NOFS/GFP_NOIO, and since I made the mistake
consintely the GFP_FS annotation was still consistent, but simply for
GFP_NOFS. Oops.

Will fix in the next version.

> > +                     __fs_reclaim_acquire();
>
>
> #ifdef CONFIG_MMU_NOTIFIER?

Hm indeed. Will fix too.

Thanks for your review.

>
> > +
> > +             lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
> > +             lock_map_release(&__mmu_notifier_invalidate_range_start_map);
> > +
> > +     }
> >   }
> >   EXPORT_SYMBOL_GPL(fs_reclaim_acquire);
> >
> >   void fs_reclaim_release(gfp_t gfp_mask)
> >   {
> > -     if (__need_fs_reclaim(gfp_mask))
> > -             __fs_reclaim_release();
> > +     if (__need_reclaim(gfp_mask)) {
> > +             if (!(gfp_mask & __GFP_FS))
> Same here?
> > +                     __fs_reclaim_release();
> > +     }
> >   }
> >   EXPORT_SYMBOL_GPL(fs_reclaim_release);
> >   #endif
>
> One suggested test case would perhaps be to call madvise(madv_dontneed)
> on a subpart of a transhuge page. That would IIRC trigger a page split
> and interesting mmu notifier calls....

The neat thing about the mmu notifier lockdep key is that we take it
whether there's notifiers or not - it's called outside of any of these
paths. So as long as you have ever hit a hugepage split somewhen since
boot, and you've hit your driver's mmu_notifier paths, lockdep will
connect the dots. Explicit testcases for all combinations not needed
anymore. This patch here just makes sure that the same holds for
memory allocations and direct reclaim (which is a lot harder to
trigger intentionally in testcases).

That was at least the idea, seems to have caught a few things already.
-Daniel

>
> Thanks,
> Thomas
>
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

  reply index

Thread overview: 106+ 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     ` Daniel Vetter [this message]
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
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
2020-06-04  9:26       ` Chris Wilson
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
2020-06-11  8:00   ` Chris Wilson
2020-06-11  8:44     ` Dave Airlie
2020-06-11  9:01       ` [Intel-gfx] " Daniel Stone
2020-06-19  8:25         ` Chris Wilson
2020-06-19  8:51           ` Daniel Vetter
2020-06-19  9:13             ` Chris Wilson
2020-06-19  9:43               ` Daniel Vetter
2020-06-19 13:12                 ` Chris Wilson
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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