On Thu, Mar 10, 2016 at 12:10:46PM +0000, Chris Wilson wrote: > On Thu, Mar 10, 2016 at 02:01:27PM +0200, Ville Syrjälä wrote: > > On Thu, Mar 10, 2016 at 11:44:28AM +0000, Chris Wilson wrote: > > > This effectively reverts > > > > > > commit 8e5fd599eb219f1054e39b40d18b217af669eea9 > > > Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > Date: Wed Apr 9 13:28:50 2014 +0300 > > > > > > drm/i915/chv: Make CHV irq handler loop until all interrupts are consumed > > > > > > as under continuous execlists load we can saturate the IRQ handler, > > > destablising the tsc clock and triggering the NMI watchdog to declare a hung > > > CPU. > > > > > > [ 552.756051] clocksource: timekeeping watchdog on CPU0: Marking clocksource 'tsc' as unstable because the skew is too large: > > > [ 552.756080] clocksource: 'refined-jiffies' wd_now: 10003b480 wd_last: 10003b28c mask: ffffffff > > > [ 552.756091] clocksource: 'tsc' cs_now: d55d31aa50 cs_last: d17446166c mask: ffffffffffffffff > > > [ 552.756210] clocksource: Switched to clocksource refined-jiffies > > > [ 575.217870] NMI watchdog: Watchdog detected hard LOCKUP on cpu 1 > > > [ 575.217893] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.5.0-rc7+ #18 > > > [ 575.217905] Hardware name: /NUC5CPYB, BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015 > > > [ 575.217915] 0000000000000000 ffff88027fd05bc0 ffffffff81288c6d 0000000000000000 > > > [ 575.217935] 0000000000000001 ffff88027fd05be0 ffffffff810e72d1 0000000000000000 > > > [ 575.217951] ffff88027fd05c80 ffff88027fd05c20 ffffffff81114b60 0000000181015f1e > > > [ 575.217967] Call Trace: > > > [ 575.217973] <NMI> [<ffffffff81288c6d>] dump_stack+0x4f/0x72 > > > [ 575.217994] [<ffffffff810e72d1>] watchdog_overflow_callback+0x151/0x160 > > > [ 575.218003] [<ffffffff81114b60>] __perf_event_overflow+0xa0/0x1e0 > > > [ 575.218016] [<ffffffff811154c4>] perf_event_overflow+0x14/0x20 > > > [ 575.218028] [<ffffffff8101d2ca>] intel_pmu_handle_irq+0x1da/0x460 > > > [ 575.218042] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218052] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218064] [<ffffffff81014ae8>] perf_event_nmi_handler+0x28/0x50 > > > [ 575.218075] [<ffffffff81007540>] nmi_handle+0x60/0x130 > > > [ 575.218086] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218096] [<ffffffff810079c0>] do_nmi+0x140/0x470 > > > [ 575.218108] [<ffffffff81559ec7>] end_repeat_nmi+0x1a/0x1e > > > [ 575.218119] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218129] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218139] [<ffffffff814a8aae>] ? poll_idle+0x3e/0x70 > > > [ 575.218148] <<EOE>> [<ffffffff814a8353>] cpuidle_enter_state+0xf3/0x2f0 > > > [ 575.218164] [<ffffffff814a8587>] cpuidle_enter+0x17/0x20 > > > [ 575.218175] [<ffffffff810aaa3a>] call_cpuidle+0x2a/0x40 > > > [ 575.218185] [<ffffffff810aade3>] cpu_startup_entry+0x273/0x330 > > > [ 575.218196] [<ffffffff81033a1e>] start_secondary+0x10e/0x130 > > > > > > However, not servicing all available IIR within the handler does hurt the > > > throughput of pathological nop execbuf by about 20%, with a similar effect > > > upon the dispatch latency of a series of execbuf. > > > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93467 > > > Testcase: igt/gem_exec_nop/basic # requires NMI watchdog > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > Cc: Antti Koskipää <antti.koskipaa@xxxxxxxxxxxxxxx > > > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > --- > > > drivers/gpu/drm/i915/i915_irq.c | 40 +++++++++++++++++++--------------------- > > > 1 file changed, 19 insertions(+), 21 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > > > index 53e5104964b3..8a3230427884 100644 > > > --- a/drivers/gpu/drm/i915/i915_irq.c > > > +++ b/drivers/gpu/drm/i915/i915_irq.c > > > @@ -1829,35 +1829,33 @@ static irqreturn_t cherryview_irq_handler(int irq, void *arg) > > > /* IRQs are synced during runtime_suspend, we don't require a wakeref */ > > > disable_rpm_wakeref_asserts(dev_priv); > > > > > > - for (;;) { > > > - master_ctl = I915_READ(GEN8_MASTER_IRQ) & ~GEN8_MASTER_IRQ_CONTROL; > > > - iir = I915_READ(VLV_IIR); > > > + master_ctl = I915_READ(GEN8_MASTER_IRQ) & ~GEN8_MASTER_IRQ_CONTROL; > > > + iir = I915_READ(VLV_IIR); > > > > > > - if (master_ctl == 0 && iir == 0) > > > - break; > > > + if (master_ctl == 0 && iir == 0) > > > + break; > > > > goto something? > > Sigh. The problem of rewriting the "obvious" patch against -nightly. I > just changed the for(;;) into do {} while(0) for testing. Perhaps I > should stick with that in case we need to flip flop agin. > > > Apart from that I have no objections if it doesn't cause problems > > with interrupts getting lost and whatnot. That was the original reason > > for it I think, but at least I myself never really looked into it. IIRC > > Rafael just told me they needed to do it to get the thing working, so > > I just put the patch in. And that was before I had even seen any silicon. > > My testing only looks at the GT side, and we do stress that pretty hard > because of execlists and have reasonable methods of detection if we stop > processing execbuf. I'm more worried about the display and pipe interrupts. IIRC GT was where the problem was originally. And just as a side note, I do have a branch somewhere that rewrites all the gmch irq handlers to not loop. Just never actually found the time to really run it on anything :) So I like moving towards that direction in any case. -- Ville Syrjälä Intel OTC -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html