On Tue, Jun 16, 2015 at 04:46:05PM +0100, Tomas Elf wrote: > On 16/06/2015 14:44, Daniel Vetter wrote: > >On Mon, Jun 08, 2015 at 06:03:19PM +0100, Tomas Elf wrote: > >>When submitting semaphores in execlist mode the hang checker crashes in this > >>function because it is only runnable in ring submission mode. The reason this > >>is of particular interest to the TDR patch series is because we use semaphores > >>as a mean to induce hangs during testing (which is the recommended way to > >>induce hangs for gen8+). It's not clear how this is supposed to work in > >>execlist mode since: > >> > >>1. This function requires a ring buffer. > >> > >>2. Retrieving a ring buffer in execlist mode requires us to retrieve the > >>corresponding context, which we get from a request. > >> > >>3. Retieving a request from the hang checker is not straight-forward since that > >>requires us to grab the struct_mutex in order to synchronize against the > >>request retirement thread. > >> > >>4. Grabbing the struct_mutex from the hang checker is nothing that we will do > >>since that puts us at risk of deadlock since a hung thread might be holding the > >>struct_mutex already. > >> > >>Therefore it's not obvious how we're supposed to deal with this. For now, we're > >>doing an early exit from this function, which avoids any kernel panic situation > >>when running our own internal TDR ULT. > >> > >>Signed-off-by: Tomas Elf <tomas.elf@xxxxxxxxx> > > > >We should have a Testcase: line here which mentions the igt testcase which > >provoke this bug. Or we need to fill this gap asap. > >-Daniel > > You know this better than I do: Is there an IGT test that submits a > semaphore in execlist mode? Because that's all you need to do to > reproduce this. We could certainly add one if there is none like > that already. No, we don't have anything submitting a hanging semaphore from userspace or igt specifically. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
