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<body><span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI] igt@perf_pmu@rc6 - dmesg-warn - BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1034 -> BUG: scheduling while atomic: perf_pmu/1513/0x00000004 -> DEBUG_LOCKS_WARN_ON(val > preempt_count())"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104943">bug 104943</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>FIXED
</td>
</tr></table>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI] igt@perf_pmu@rc6 - dmesg-warn - BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1034 -> BUG: scheduling while atomic: perf_pmu/1513/0x00000004 -> DEBUG_LOCKS_WARN_ON(val > preempt_count())"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104943#c1">Comment # 1</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI] igt@perf_pmu@rc6 - dmesg-warn - BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1034 -> BUG: scheduling while atomic: perf_pmu/1513/0x00000004 -> DEBUG_LOCKS_WARN_ON(val > preempt_count())"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104943">bug 104943</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>commit b2f78cda260bc6a1a2d382b1d85a29e69b5b3724
Author: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Date: Mon Feb 5 09:34:48 2018 +0000
drm/i915/pmu: Fix PMU enable vs execlists tasklet race
Commit 99e48bf98dd0 ("drm/i915: Lock out execlist tasklet while peeking
inside for busy-stats") added a tasklet_disable call in busy stats
enabling, but we failed to understand that the PMU enable callback runs
as an hard IRQ (IPI).
Consequence of this is that the PMU enable callback can interrupt the
execlists tasklet, and will then deadlock when it calls
intel_engine_stats_enable->tasklet_disable.
To fix this, I realized it is possible to move the engine stats enablement
and disablement to PMU event init and destroy hooks. This allows for much
simpler implementation since those hooks run in normal context (can
sleep).
v2: Extract engine_event_destroy. (Chris Wilson)
Signed-off-by: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Fixes: 99e48bf98dd0 ("drm/i915: Lock out execlist tasklet while peeking
inside for busy-stats")
Testcase: igt/perf_pmu/enable-race-*
Cc: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Cc: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Cc: Jani Nikula <<a href="mailto:jani.nikula@linux.intel.com">jani.nikula@linux.intel.com</a>>
Cc: Joonas Lahtinen <<a href="mailto:joonas.lahtinen@linux.intel.com">joonas.lahtinen@linux.intel.com</a>>
Cc: Rodrigo Vivi <<a href="mailto:rodrigo.vivi@intel.com">rodrigo.vivi@intel.com</a>>
Cc: <a href="mailto:intel-gfx@lists.freedesktop.org">intel-gfx@lists.freedesktop.org</a>
Reviewed-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Link:
<a href="https://patchwork.freedesktop.org/patch/msgid/20180205093448.13877-1-tvrtko.ursulin@linux.intel.com">https://patchwork.freedesktop.org/patch/msgid/20180205093448.13877-1-tvrtko.ursulin@linux.intel.com</a></pre>
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