drm/i915: Prevent timeline updates whilst performing reset

As the fence may be signaled concurrently from an interrupt on another
device, it is possible for the list of requests on the timeline to be
modified as we walk it. Take both (the context's timeline and the global
timeline) locks to prevent such modifications.

Fixes: 80b204bce8f2 ("drm/i915: Enable multiple timelines")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161223145804.6605-10-chris@chris-wilson.co.uk
(cherry picked from commit 00c25e3f40083a6d5f1111955baccd287ee49258)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 5d146f9f4aad505ef0f591a9c84e99e191ae2290..1e505d30b71ea4a1db0076bc2a1df19c7d71b341 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2730,6 +2730,7 @@ static void i915_gem_reset_engine(struct intel_engine_cs *engine)
        struct drm_i915_gem_request *request;
        struct i915_gem_context *incomplete_ctx;
        struct intel_timeline *timeline;
+       unsigned long flags;
        bool ring_hung;
 
        if (engine->irq_seqno_barrier)
@@ -2765,13 +2766,20 @@ static void i915_gem_reset_engine(struct intel_engine_cs *engine)
        if (i915_gem_context_is_default(incomplete_ctx))
                return;
 
+       timeline = i915_gem_context_lookup_timeline(incomplete_ctx, engine);
+
+       spin_lock_irqsave(&engine->timeline->lock, flags);
+       spin_lock(&timeline->lock);
+
        list_for_each_entry_continue(request, &engine->timeline->requests, link)
                if (request->ctx == incomplete_ctx)
                        reset_request(request);
 
-       timeline = i915_gem_context_lookup_timeline(incomplete_ctx, engine);
        list_for_each_entry(request, &timeline->requests, link)
                reset_request(request);
+
+       spin_unlock(&timeline->lock);
+       spin_unlock_irqrestore(&engine->timeline->lock, flags);
 }
 
 void i915_gem_reset(struct drm_i915_private *dev_priv)