On 03/12/2020 10:34, Chris Wilson wrote:
In the course of discovering and closing many races with context closure and execbuf submission, since commit 61231f6bd056 ("drm/i915/gem: Check that the context wasn't closed during setup") we started checking that the context was not closed by another userspace thread during the execbuf ioctl. In doing so we cancelled the inflight request (by telling it to be skipped), but kept reporting success since we do submit a request, albeit one that doesn't execute. As the error is known before we return from the ioctl, we can report the error we detect immediately, rather than leave it on the fence status. With the immediate propagation of the error, it is easier for userspace to handle.
Fixes: 61231f6bd056 ("drm/i915/gem: Check that the context wasn't closed during setup") Testcase: igt/gem_ctx_exec/basic-close-race Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: stable@vger.kernel.org # v5.7+
drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 1904e6e5ea64..b07dc1156a0e 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -3097,7 +3097,7 @@ static void retire_requests(struct intel_timeline *tl, struct i915_request *end) break; } -static void eb_request_add(struct i915_execbuffer *eb) +static int eb_request_add(struct i915_execbuffer *eb, int err) { struct i915_request *rq = eb->request; struct intel_timeline * const tl = i915_request_timeline(rq); @@ -3118,6 +3118,7 @@ static void eb_request_add(struct i915_execbuffer *eb) /* Serialise with context_close via the add_to_timeline */ i915_request_set_error_once(rq, -ENOENT); __i915_request_skip(rq);
err = -ENOENT; /* override any transient errors */__i915_request_queue(rq, &attr); @@ -3127,6 +3128,8 @@ static void eb_request_add(struct i915_execbuffer *eb) retire_requests(tl, prev); mutex_unlock(&tl->mutex);
- return err; }
static const i915_user_extension_fn execbuf_extensions[] = { @@ -3332,7 +3335,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, err = eb_submit(&eb, batch); err_request: i915_request_get(eb.request);
- eb_request_add(&eb);
- err = eb_request_add(&eb, err);
if (eb.fences) signal_fence_array(&eb);
Simple enough and it explains why gem_busy assert in the IGT can fail after execbuf succeeded - skipped request executes before the check since the payload was zapped. Fast timing but obviously possible.
Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com
Regards,
Tvrtko