On Thu, Feb 16, 2017 at 03:17:30PM +0200, Mika Kuoppala wrote: > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > > > If an interrupt has been posted, and we were spinning on the active > > seqno waiting for it to advance but it did not, then we can expect that > > it will not see its advance in the immediate future > > Why we can expect this? The seqno is meant to arrive *before* the interrupt. The check is lazy, but assume it is irq_posted = test_bit(ENGINE_IRQ_BREADCRUMB, &req->engine->irq_posted); if (seqno_passed()) return true; if (irq_posted) return false; with the strong read ordering imposed. The reason why I think we can be lax is that we expect the caller to check after spin_request reports false (just it may do some other work in the meantime). Note that the interrupt will only be detected if there is already a waiter (or equivalent). -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
