Tim Gore Intel Corporation (UK) Ltd. - Co. Reg. #1134945 - Pipers Way, Swindon SN3 1RJ > -----Original Message----- > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of Daniel > Vetter > Sent: Tuesday, July 14, 2015 9:09 AM > To: Gore, Tim > Cc: Daniel Vetter; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Wood, Thomas > Subject: Re: [PATCH i-g-t] lib/igt_gt.c : allow changes to stop_rings > mode bits > > On Mon, Jul 13, 2015 at 04:07:14PM +0000, Gore, Tim wrote: > > > > > > Tim Gore > > Intel Corporation (UK) Ltd. - Co. Reg. #1134945 - Pipers Way, Swindon > > SN3 1RJ > > > > > > > -----Original Message----- > > > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of > > > Daniel Vetter > > > Sent: Monday, July 13, 2015 3:59 PM > > > To: Gore, Tim > > > Cc: Daniel Vetter; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Wood, Thomas > > > Subject: Re: [PATCH i-g-t] lib/igt_gt.c : allow changes > > > to stop_rings mode bits > > > > > > On Mon, Jul 13, 2015 at 09:43:11AM +0000, Gore, Tim wrote: > > > > > > > > > > > > Tim Gore > > > > Intel Corporation (UK) Ltd. - Co. Reg. #1134945 - Pipers Way, > > > > Swindon > > > > SN3 1RJ > > > > > > > > > -----Original Message----- > > > > > From: Daniel Vetter [mailto:daniel.vetter@xxxxxxxx] On Behalf Of > > > > > Daniel Vetter > > > > > Sent: Monday, July 13, 2015 10:30 AM > > > > > To: Gore, Tim > > > > > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Wood, Thomas > > > > > Subject: Re: [PATCH i-g-t] lib/igt_gt.c : allow > > > > > changes to stop_rings mode bits > > > > > > > > > > On Fri, Jul 10, 2015 at 02:06:06PM +0100, tim.gore@xxxxxxxxx wrote: > > > > > > From: Tim Gore <tim.gore@xxxxxxxxx> > > > > > > > > > > > > In function igt_set_stop_rings, the test > > > > > > igt_assert_f(flags == 0 || current == 0, .. > > > > > > > > > > > > will fail if we are trying to force a hang but the > > > > > > STOP_RINGS_ALLOW_BAN or STOP_RINGS_ALLOW_ERROR bit is > set. > > > > > > With the introduction of per ring resets in the driver (in > > > > > > android) these bits do not get cleared to zero when an > > > > > > individual ring is reset. This causes subsequent attempt to > > > > > > cause a ring hang via this function to fail, leading to > > > > > > several igt tests failing (ie gem_reset_stats subtest ban-xxx etc). > > > > > > > > > > Fix tdr to reset these instead? > > > > > -Daniel > > > > > > > > > I could change tdr, but why. When the TDR handles a ring hang and > > > > resets the ring, why would it modify the flag that defines if the > > > > driver should ban a frequently hanging context? If we get rid of > > > > the stop_rings interface, as Chris Wilson suggested, we would > > > > still need to keep the STOP_RING_ALLOW_BAN/ALLOW_ERRORS bits in > > > > debugfs, but > > > you > > > > would not expect to have to re-write these bits each time there is > > > > a ring > > > reset. > > > > > > The fix current hang recover code to no reset this, add some grace > > > period, then push this patch to igt. We don't have full-blown abi > > > guarantees for debugfs/igt stuff, but I want at least a few months > > > (really last released > > > kernel&igt) of backwards/forward compatibility. And inconsistent > > > behaviour isn't great imo. > > > -Daniel > > > > Sorry Daniel, I didn't really follow that. > > I didn't want a gpu reset to clear the ALLOW_BAN bit, since this will > > defeat the point of this bit, except perhaps in test situations where > > you can keep setting it each time you deliberately cause a hang. It > > seems like the ALLOW_BAN bit has uses in real world situations, although I > don't know it anyone uses it. > > ALLOW_BAN is only for testing. It's meant to re-enable auto-banning > because we disable that by default for automated tests. This is all meant to > be used together with the stop_rings stuff only. > > > Would you be more comfortable with > > Igt_assert_f ( ( flags ==0 ) || > > (( current & STOP_RING_ALL) ==0) && ((current ^ flags) & ~ > > STOP_RING_ALL == 0 ) ) > > > > So the either the new flags must be 0 (currently allowed) or the > > existing flags must indicate that all hangs are cleared (0 except > > possibly the mode bits) AND the mode bits you are writing are the same as > the current values. ?? > > Iirc gem_reset_stats uses stop_rings only to supress gpu reset warnings in > dmesg (since they're expected) and not for the actual stop_rings logic. It sets > stop_rings after submitting the hanging batch, but before that one is > detected as hung. We could just add another bit to stop_rings for that case. > > What I still don't understand is why tdr can't just keep on properly resetting > stop_rings. It'll break tons of existing tests, and I don't understand the > upside. stop_rings has become quasi-abi (that's why the ALLOW bits have > such funky semantics, it's for backwards compat), if you need to change it > you need to extend it, not break it. > -Daniel > -- OK, I hadn't spotted that it was a debug only flag. In that case it is just up to the tests to keep setting it. It only seems to be used in gem_reset_stats anyway. So I'll change TDR to clear ALLOW_BAN/WARN when stop_bits gets cleared to 0. Tim > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
