[PATCH] drm/i915: Mark vm_free_page() as a potential sleeper agent

[PATCH] drm/i915: Mark vm_free_page() as a potential sleeper agent

[Chris Wilson]

vm_free_page() may call down into set_pages_array_wb() (which itself
sleeps, on x86 at least) but only if on !llc and the caches overflow.
Since this is unlikely, we only rarely trigger the error in practice,
and so to make CI detection of this sleeping bug possible we want to
mark the common vm_free_page() as a potential sleep.

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 2847a6b41c16..1e40eeb31f9d 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -454,6 +454,14 @@ static void vm_free_pages_release(struct i915_address_space *vm,
 
 static void vm_free_page(struct i915_address_space *vm, struct page *page)
 {
+	/*
+	 * On !llc, we need to change the pages back to WB. We only do so
+	 * in bulk, so we rarely need to change the page attributes here,
+	 * but doing so requires a stop_machine() from deep inside arch/x86/mm.
+	 * To make detection of the possible sleep more likely, use an
+	 * unconditional might_sleep() for everybody.
+	 */
+	might_sleep();
 	if (!pagevec_add(&vm->free_pages, page))
 		vm_free_pages_release(vm, false);
 }
-- 
2.15.0

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Re: [PATCH] drm/i915: Mark vm_free_page() as a potential sleeper agent

[Chris Wilson]

Quoting Chris Wilson (2017-11-09 10:21:41)
> vm_free_page() may call down into set_pages_array_wb() (which itself
> sleeps, on x86 at least) but only if on !llc and the caches overflow.
> Since this is unlikely, we only rarely trigger the error in practice,
> and so to make CI detection of this sleeping bug possible we want to
> mark the common vm_free_page() as a potential sleep.
> 

References: https://bugs.freedesktop.org/show_bug.cgi?id=103638
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Matthew Auld <matthew.william.auld@gmail.com>

The real test ofc is whether this reports an error from CI.
-Chris
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✗ Fi.CI.BAT: warning for drm/i915: Mark vm_free_page() as a potential sleeper agent

[Patchwork]

== Series Details ==

Series: drm/i915: Mark vm_free_page() as a potential sleeper agent
URL   : https://patchwork.freedesktop.org/series/33503/
State : warning

== Summary ==

Series 33503v1 drm/i915: Mark vm_free_page() as a potential sleeper agent
https://patchwork.freedesktop.org/api/1.0/series/33503/revisions/1/mbox/

Test chamelium:
        Subgroup dp-crc-fast:
                pass       -> FAIL       (fi-kbl-7500u) fdo#102514
Test gem_ctx_basic:
                fail       -> SKIP       (fi-gdg-551)
Test gem_ctx_switch:
        Subgroup basic-default:
                pass       -> DMESG-WARN (fi-bdw-5557u)
                pass       -> DMESG-WARN (fi-bdw-gvtdvm)
        Subgroup basic-default-heavy:
                pass       -> DMESG-WARN (fi-skl-6600u)
Test gem_exec_reloc:
        Subgroup basic-cpu-gtt-active:
                fail       -> PASS       (fi-gdg-551) fdo#102582 +2
Test gem_sync:
        Subgroup basic-store-all:
                fail       -> PASS       (fi-ivb-3520m) fdo#100007

fdo#102514 https://bugs.freedesktop.org/show_bug.cgi?id=102514
fdo#102582 https://bugs.freedesktop.org/show_bug.cgi?id=102582
fdo#100007 https://bugs.freedesktop.org/show_bug.cgi?id=100007

fi-bdw-5557u     total:289  pass:267  dwarn:1   dfail:0   fail:0   skip:21  time:441s
fi-bdw-gvtdvm    total:289  pass:264  dwarn:1   dfail:0   fail:0   skip:24  time:457s
fi-blb-e6850     total:289  pass:223  dwarn:1   dfail:0   fail:0   skip:65  time:379s
fi-bsw-n3050     total:289  pass:243  dwarn:0   dfail:0   fail:0   skip:46  time:544s
fi-bwr-2160      total:289  pass:183  dwarn:0   dfail:0   fail:0   skip:106 time:273s
fi-bxt-dsi       total:289  pass:259  dwarn:0   dfail:0   fail:0   skip:30  time:506s
fi-bxt-j4205     total:289  pass:260  dwarn:0   dfail:0   fail:0   skip:29  time:505s
fi-byt-j1900     total:289  pass:254  dwarn:0   dfail:0   fail:0   skip:35  time:501s
fi-byt-n2820     total:289  pass:250  dwarn:0   dfail:0   fail:0   skip:39  time:487s
fi-elk-e7500     total:289  pass:229  dwarn:0   dfail:0   fail:0   skip:60  time:427s
fi-gdg-551       total:289  pass:176  dwarn:1   dfail:0   fail:3   skip:109 time:265s
fi-glk-1         total:289  pass:261  dwarn:0   dfail:0   fail:0   skip:28  time:539s
fi-hsw-4770      total:289  pass:262  dwarn:0   dfail:0   fail:0   skip:27  time:430s
fi-hsw-4770r     total:289  pass:262  dwarn:0   dfail:0   fail:0   skip:27  time:444s
fi-ilk-650       total:289  pass:228  dwarn:0   dfail:0   fail:0   skip:61  time:426s
fi-ivb-3520m     total:289  pass:260  dwarn:0   dfail:0   fail:0   skip:29  time:482s
fi-ivb-3770      total:289  pass:260  dwarn:0   dfail:0   fail:0   skip:29  time:467s
fi-kbl-7500u     total:289  pass:263  dwarn:1   dfail:0   fail:1   skip:24  time:465s
fi-kbl-7560u     total:289  pass:270  dwarn:0   dfail:0   fail:0   skip:19  time:525s
fi-kbl-7567u     total:289  pass:269  dwarn:0   dfail:0   fail:0   skip:20  time:480s
fi-kbl-r         total:289  pass:262  dwarn:0   dfail:0   fail:0   skip:27  time:534s
fi-pnv-d510      total:289  pass:222  dwarn:1   dfail:0   fail:0   skip:66  time:567s
fi-skl-6260u     total:289  pass:269  dwarn:0   dfail:0   fail:0   skip:20  time:454s
fi-skl-6600u     total:289  pass:261  dwarn:1   dfail:0   fail:0   skip:27  time:545s
fi-skl-6700hq    total:289  pass:263  dwarn:0   dfail:0   fail:0   skip:26  time:563s
fi-skl-6700k     total:289  pass:265  dwarn:0   dfail:0   fail:0   skip:24  time:516s
fi-skl-6770hq    total:289  pass:269  dwarn:0   dfail:0   fail:0   skip:20  time:491s
fi-skl-gvtdvm    total:289  pass:266  dwarn:0   dfail:0   fail:0   skip:23  time:458s
fi-snb-2520m     total:289  pass:250  dwarn:0   dfail:0   fail:0   skip:39  time:568s
fi-snb-2600      total:289  pass:249  dwarn:0   dfail:0   fail:0   skip:40  time:418s
Blacklisted hosts:
fi-cnl-y         total:289  pass:262  dwarn:0   dfail:0   fail:0   skip:27  time:553s
fi-glk-dsi       total:289  pass:259  dwarn:0   dfail:0   fail:0   skip:30  time:491s

65dc54b704d3ee0486f9f5b11f00c28973f783a2 drm-tip: 2017y-11m-09d-08h-53m-46s UTC integration manifest
2a794913c1f6 drm/i915: Mark vm_free_page() as a potential sleeper agent

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_7031/
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Re: [PATCH] drm/i915: Mark vm_free_page() as a potential sleeper agent

[Daniel Vetter]

On Thu, Nov 09, 2017 at 10:23:44AM +0000, Chris Wilson wrote:
> Quoting Chris Wilson (2017-11-09 10:21:41)
> > vm_free_page() may call down into set_pages_array_wb() (which itself
> > sleeps, on x86 at least) but only if on !llc and the caches overflow.
> > Since this is unlikely, we only rarely trigger the error in practice,
> > and so to make CI detection of this sleeping bug possible we want to
> > mark the common vm_free_page() as a potential sleep.
> > 
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=103638
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > Cc: Matthew Auld <matthew.william.auld@gmail.com>
> 
> The real test ofc is whether this reports an error from CI.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

But if it indeed blows up on CI I think it'd be good to fix first, then
apply the more aggressive debug check. Otherwise CI and Marta will be on
fire :-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH] drm/i915: Mark vm_free_page() as a potential sleeper agent

[Chris Wilson]

Quoting Daniel Vetter (2017-11-09 10:46:41)
> On Thu, Nov 09, 2017 at 10:23:44AM +0000, Chris Wilson wrote:
> > Quoting Chris Wilson (2017-11-09 10:21:41)
> > > vm_free_page() may call down into set_pages_array_wb() (which itself
> > > sleeps, on x86 at least) but only if on !llc and the caches overflow.
> > > Since this is unlikely, we only rarely trigger the error in practice,
> > > and so to make CI detection of this sleeping bug possible we want to
> > > mark the common vm_free_page() as a potential sleep.
> > > 
> > 
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=103638
> > > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > > Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > > Cc: Matthew Auld <matthew.william.auld@gmail.com>
> > 
> > The real test ofc is whether this reports an error from CI.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> But if it indeed blows up on CI I think it'd be good to fix first, then
> apply the more aggressive debug check. Otherwise CI and Marta will be on
> fire :-)

It got a few more hits, but not across the board as I was hoping. The
next place is i915_vma_unbind(). That is always a potential sleeper due
to its implicit wait on the GPU.
-Chris
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✓ Fi.CI.IGT: success for drm/i915: Mark vm_free_page() as a potential sleeper agent

[Patchwork]

== Series Details ==

Series: drm/i915: Mark vm_free_page() as a potential sleeper agent
URL   : https://patchwork.freedesktop.org/series/33503/
State : success

== Summary ==

Test kms_cursor_legacy:
        Subgroup flip-vs-cursor-atomic-transitions:
                pass       -> FAIL       (shard-hsw) fdo#102670
Test kms_plane:
        Subgroup plane-position-hole-dpms-pipe-c-planes:
                skip       -> PASS       (shard-hsw)
Test kms_rotation_crc:
        Subgroup primary-rotation-180:
                skip       -> PASS       (shard-hsw)
Test kms_pipe_crc_basic:
        Subgroup nonblocking-crc-pipe-a:
                skip       -> PASS       (shard-hsw)
Test kms_setmode:
        Subgroup basic:
                fail       -> PASS       (shard-hsw) fdo#99912
Test perf:
        Subgroup blocking:
                pass       -> FAIL       (shard-hsw) fdo#102252
Test pm_lpsp:
        Subgroup screens-disabled:
                fail       -> PASS       (shard-hsw) fdo#102579

fdo#102670 https://bugs.freedesktop.org/show_bug.cgi?id=102670
fdo#99912 https://bugs.freedesktop.org/show_bug.cgi?id=99912
fdo#102252 https://bugs.freedesktop.org/show_bug.cgi?id=102252
fdo#102579 https://bugs.freedesktop.org/show_bug.cgi?id=102579

shard-hsw        total:2540 pass:1432 dwarn:0   dfail:0   fail:11  skip:1097 time:9315s

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_7031/shards.html
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