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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2013-07-09 09:22:39 +0100 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2013-07-10 10:41:55 +0200 |
| commit | 02978ff57a5bdfbf703d2bc5a4d933a53ede3144 (patch) | |
| tree | d670634cd62c3e5fd6bb71c24157a1cecf98786a /drivers/gpu/drm | |
| parent | c11e5f35ab490bd30591563816fbc83526521777 (diff) | |
| download | linux-02978ff57a5bdfbf703d2bc5a4d933a53ede3144.tar.bz2 | |
drm/i915: Fix write-read race with multiple rings
Daniel noticed a problem where is we wrote to an object with ring A in
the middle of a very long running batch, then executed a quick batch on
ring B before a batch that reads from the same object, its obj->ring would
now point to ring B, but its last_write_seqno would be still relative to
ring A. This would allow for the user to read from the object before the
GPU had completed the write, as set_domain would only check that ring B
had passed the last_write_seqno.
To fix this simply (and inelegantly), we bump the last_write_seqno when
switching rings so that the last_write_seqno is always relative to the
current obj->ring.
This fixes igt/tests/gem_write_read_ring_switch.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
[danvet: Add note about the newly created igt which exercises this
bug.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 7f368d79f7d2..8fd8e82ebda4 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1880,6 +1880,10 @@ i915_gem_object_move_to_active(struct drm_i915_gem_object *obj, u32 seqno = intel_ring_get_seqno(ring); BUG_ON(ring == NULL); + if (obj->ring != ring && obj->last_write_seqno) { + /* Keep the seqno relative to the current ring */ + obj->last_write_seqno = seqno; + } obj->ring = ring; /* Add a reference if we're newly entering the active list. */ |