On Wed, Feb 22, 2017 at 12:29:00PM +0000, Tvrtko Ursulin wrote: > > On 22/02/2017 11:46, Chris Wilson wrote: > >A request is assigned a global seqno only when it is on the hardware > >execution queue. The global seqno can be used to maintain a list of > >requests on the same engine in retirement order, for example for > >constructing a priority queue for waiting. Prior to its execution, or > >if it is subsequently removed in the event of preemption, its global > >seqno is zero. As both insertion and removal from the execution queue > >may operate in IRQ context, it is not guarded by the usual struct_mutex > >BKL. Instead those relying on the global seqno must be prepared for its > >value to change between reads. Only when the request is complete can > >the global seqno be stable (due to the memory barriers on submitting > >the commands to the hardware to write the breadcrumb, if the HWS shows > >that it has passed the global seqno and the global seqno is unchanged > >after the read, it is indeed complete). > > Missed some questions I've raised on this one in the previous round. Just missed it when scanning for opens from the threads. > I never got round re-reading it if you were waiting for that by any chance. Looks like it is one you have to read after seeing where the series goes. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
