From: Chris Wilson Date: Fri, 29 Nov 2019 15:18:45 +0000 (+0000) Subject: drm/i915/gem: Take timeline->mutex to walk list-of-requests X-Git-Tag: v5.5-rc1~28^2^2~2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=3ee1a9f5d0bc0e9dbac5b014e2e8a7d540b836df;p=linux.git drm/i915/gem: Take timeline->mutex to walk list-of-requests Though the context is closed and so no more requests can be added to the timeline, retirement can still be removing requests. It can even be removing the very request we are inspecting and so cause us to wander into dead links. Serialise with the retirement by taking the timeline->mutex used for guarding the timeline->requests list. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112404 Fixes: 4a3174152147 ("drm/i915/gem: Refine occupancy test in kill_context()") Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Mika Kuoppala Cc: Matthew Auld Cc: Joonas Lahtinen Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20191129151845.1092933-1-chris@chris-wilson.co.uk (cherry picked from commit 7ce596a8036cf3a4cb9ffa0c4edd8a76a7a43cc3) Signed-off-by: Joonas Lahtinen --- diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 255ab040022e..4237a2887ff2 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -368,7 +368,7 @@ static struct intel_engine_cs *active_engine(struct intel_context *ce) if (!ce->timeline) return NULL; - rcu_read_lock(); + mutex_lock(&ce->timeline->mutex); list_for_each_entry_reverse(rq, &ce->timeline->requests, link) { if (i915_request_completed(rq)) break; @@ -378,7 +378,7 @@ static struct intel_engine_cs *active_engine(struct intel_context *ce) if (engine) break; } - rcu_read_unlock(); + mutex_unlock(&ce->timeline->mutex); return engine; }