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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][DRMTIP] igt@gem_userptr_blits@coherency-sync - dmesg-warn - WARNING: possible circular locking dependency detected"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108375">bug 108375</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>
<p>
<div>
<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][DRMTIP] igt@gem_userptr_blits@coherency-sync - dmesg-warn - WARNING: possible circular locking dependency detected"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108375#c3">Comment # 3</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][DRMTIP] igt@gem_userptr_blits@coherency-sync - dmesg-warn - WARNING: possible circular locking dependency detected"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108375">bug 108375</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 484d9a844d0d0aeaa4cd3cec20885b7de9986a55 (HEAD -> drm-intel-next-queued,
drm-intel/for-linux-next, drm-intel/drm-intel-next-queued)
Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>>
Date: Tue Jan 15 12:44:42 2019 +0000
drm/i915/userptr: Avoid struct_mutex recursion for
mmu_invalidate_range_start
Since commit 93065ac753e4 ("mm, oom: distinguish blockable mode for mmu
notifiers") we have been able to report failure from
mmu_invalidate_range_start which allows us to use a trylock on the
struct_mutex to avoid potential recursion and report -EBUSY instead.
Furthermore, this allows us to pull the work into the main callback and
avoid the sleight-of-hand in using a workqueue to avoid lockdep.
However, not all paths to mmu_invalidate_range_start are prepared to
handle failure, so instead of reporting the recursion, deal with it by
propagating the failure upwards, who can decide themselves to handle it
or report it.
v2: Mark up the recursive lock behaviour and comment on the various weak
points.
v3: Follow commit 3824e41975ae ("drm/i915: Use mutex_lock_killable() from
inside the shrinker") and also use mutex_lock_killable().
v3.1: No leak on EINTR.
Bugzilla: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - [CI][DRMTIP] igt@gem_userptr_blits@coherency-sync - dmesg-warn - WARNING: possible circular locking dependency detected"
href="show_bug.cgi?id=108375">https://bugs.freedesktop.org/show_bug.cgi?id=108375</a>
References: 93065ac753e4 ("mm, oom: distinguish blockable mode for mmu
notifiers")
Signed-off-by: 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>>
Reviewed-by: Tvrtko Ursulin <<a href="mailto:tvrtko.ursulin@intel.com">tvrtko.ursulin@intel.com</a>>
Link:
<a href="https://patchwork.freedesktop.org/patch/msgid/20190115124442.3500-1-chris@chris-wilson.co.uk">https://patchwork.freedesktop.org/patch/msgid/20190115124442.3500-1-chris@chris-wilson.co.uk</a></pre>
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