Quoting Mika Kuoppala (2020-03-02 18:29:09)
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> > @@ -491,30 +491,104 @@ static void kill_engines(struct i915_gem_engines *engines)
> > static void kill_stale_engines(struct i915_gem_context *ctx)
> > {
> > struct i915_gem_engines *pos, *next;
> > - unsigned long flags;
> >
> > - spin_lock_irqsave(&ctx->stale.lock, flags);
> > + spin_lock_irq(&ctx->stale.lock);
>
> Reader ponders why it was with flags on the first place.
Hindsight is 20/20.
> > + GEM_BUG_ON(!i915_gem_context_is_closed(ctx));
> > list_for_each_entry_safe(pos, next, &ctx->stale.engines, link) {
> > - if (!i915_sw_fence_await(&pos->fence))
> > + if (!i915_sw_fence_await(&pos->fence)) {
> > + list_del_init(&pos->link);
>
> Is this for making the bed for kill path list_empty?
It's acknowledging that if we are racing in FENCE_COMPLETE, we don't
need to kill it.
> > +static void engines_idle_release(struct i915_gem_context *ctx,
> > + struct i915_gem_engines *engines)
> > +{
> > + struct i915_gem_engines_iter it;
> > + struct intel_context *ce;
> > +
> > + i915_sw_fence_init(&engines->fence, engines_notify);
> > + INIT_LIST_HEAD(&engines->link);
> > +
> > + engines->ctx = i915_gem_context_get(ctx);
> > +
> > + for_each_gem_engine(ce, engines, it) {
> > + struct dma_fence *fence;
> > + int err = 0;
> > +
> > + /* serialises with execbuf */
> > + RCU_INIT_POINTER(ce->gem_context, NULL);
> > + if (!intel_context_pin_if_active(ce))
> > + continue;
>
> Ok so this should ensure the lifetime past the execbufs.
>
> > +
> > + fence = i915_active_fence_get(&ce->timeline->last_request);
Note it's this fence_get + ce->gem_context that combine to give us the
execbuf closure guard.
> > + if (fence) {
> > + err = i915_sw_fence_await_dma_fence(&engines->fence,
> > + fence, 0,
> > + GFP_KERNEL);
> > + dma_fence_put(fence);
> > + }
> > + intel_context_unpin(ce);
> > + if (err < 0)
> > + goto kill;
> > + }
-Chris
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