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drm/amdgpu: hold reference to fences in amdgpu_sa_bo_new (v2)

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An arbitrary amount of time can pass between spin_unlock and
fence_wait_any_timeout, so we need to ensure that nobody frees the
fences from under us.

A stress test (rapidly starting and killing hundreds of glxgears
instances) ran into a deadlock in fence_wait_any_timeout after
about an hour, and this race condition appears to be a plausible
cause.

v2: agd: rebase on upstream

Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Nicolai Hähnle 2016-02-05 10:59:43 -05:00 committed by Alex Deucher
parent ca19852884
commit a8d81b3626
1 changed files with 4 additions and 1 deletions
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5
drivers/gpu/drm/amd/amdgpu/amdgpu_sa.c
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@ -354,12 +354,15 @@ int amdgpu_sa_bo_new(struct amdgpu_sa_manager *sa_manager,
for (i = 0, count = 0; i < AMDGPU_MAX_RINGS; ++i)
if (fences[i])
fences[count++] = fences[i];
fences[count++] = fence_get(fences[i]);
if (count) {
spin_unlock(&sa_manager->wq.lock);
t = fence_wait_any_timeout(fences, count, false,
MAX_SCHEDULE_TIMEOUT);
for (i = 0; i < count; ++i)
fence_put(fences[i]);
r = (t > 0) ? 0 : t;
spin_lock(&sa_manager->wq.lock);
} else {