Chris Wilson <[email protected]> writes: > The downside of using semaphores is that we lose metadata passing > along the signaling chain. This is particularly nasty when we > need to pass along a fatal error such as EFAULT or EDEADLK. For > fatal errors we want to scrub the request before it is executed, > which means that we cannot preload the request onto HW and have > it wait upon a semaphore.
b is waiting on a, a fails and we want to release b with error? > > Signed-off-by: Chris Wilson <[email protected]> > --- > drivers/gpu/drm/i915/i915_request.c | 26 +++++++++++++++++++++ > drivers/gpu/drm/i915/i915_scheduler_types.h | 1 + > 2 files changed, 27 insertions(+) > > diff --git a/drivers/gpu/drm/i915/i915_request.c > b/drivers/gpu/drm/i915/i915_request.c > index 94189c7d43cd..f0f9393e2ade 100644 > --- a/drivers/gpu/drm/i915/i915_request.c > +++ b/drivers/gpu/drm/i915/i915_request.c > @@ -1002,6 +1002,15 @@ emit_semaphore_wait(struct i915_request *to, > if (!rcu_access_pointer(from->hwsp_cacheline)) > goto await_fence; > > + /* > + * If this or its dependents are waiting on an external fence > + * that may fail catastrophically, then we want to avoid using > + * sempahores as they bypass the fence signaling metadata, and we semaphore -Mika > + * lose the fence->error propagation. > + */ > + if (from->sched.flags & I915_SCHED_HAS_EXTERNAL_CHAIN) > + goto await_fence; > + > /* Just emit the first semaphore we see as request space is limited. */ > if (already_busywaiting(to) & mask) > goto await_fence; > @@ -1064,12 +1073,29 @@ i915_request_await_request(struct i915_request *to, > struct i915_request *from) > return ret; > } > > + if (from->sched.flags & I915_SCHED_HAS_EXTERNAL_CHAIN) > + to->sched.flags |= I915_SCHED_HAS_EXTERNAL_CHAIN; > + > return 0; > } > > +static void mark_external(struct i915_request *rq) > +{ > + /* > + * The downside of using semaphores is that we lose metadata passing > + * along the signaling chain. This is particularly nasty when we > + * need to pass along a fatal error such as EFAULT or EDEADLK. For > + * fatal errors we want to scrub the request before it is executed, > + * which means that we cannot preload the request onto HW and have > + * it wait upon a semaphore. > + */ > + rq->sched.flags |= I915_SCHED_HAS_EXTERNAL_CHAIN; > +} > + > static int > i915_request_await_external(struct i915_request *rq, struct dma_fence *fence) > { > + mark_external(rq); > return i915_sw_fence_await_dma_fence(&rq->submit, fence, > fence->context ? > I915_FENCE_TIMEOUT : 0, > I915_FENCE_GFP); > diff --git a/drivers/gpu/drm/i915/i915_scheduler_types.h > b/drivers/gpu/drm/i915/i915_scheduler_types.h > index 7186875088a0..6ab2c5289bed 100644 > --- a/drivers/gpu/drm/i915/i915_scheduler_types.h > +++ b/drivers/gpu/drm/i915/i915_scheduler_types.h > @@ -66,6 +66,7 @@ struct i915_sched_node { > struct i915_sched_attr attr; > unsigned int flags; > #define I915_SCHED_HAS_SEMAPHORE_CHAIN BIT(0) > +#define I915_SCHED_HAS_EXTERNAL_CHAIN BIT(1) > intel_engine_mask_t semaphores; > }; > > -- > 2.20.1 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
