On 05/08/2018 08:35 AM, Chris Wilson wrote:
CI noticed
<4>[ 23.430701] ============================================
<4>[ 23.430706] WARNING: possible recursive locking detected
<4>[ 23.430713] 4.17.0-rc4-CI-CI_DRM_4156+ #1 Not tainted
<4>[ 23.430720] --------------------------------------------
<4>[ 23.430725] systemd-udevd/169 is trying to acquire lock:
<4>[ 23.430732] (ptrval) (&(&timeline->lock)->rlock){....}, at: move_to_timeline+0x48/0x12c [i915]
<4>[ 23.430888]
but task is already holding lock:
<4>[ 23.430894] (ptrval) (&(&timeline->lock)->rlock){....}, at: i915_request_submit+0x1a/0x40 [i915]
<4>[ 23.430995]
other info that might help us debug this:
<4>[ 23.431002] Possible unsafe locking scenario:
<4>[ 23.431007] CPU0
<4>[ 23.431010] ----
<4>[ 23.431013] lock(&(&timeline->lock)->rlock);
<4>[ 23.431021] lock(&(&timeline->lock)->rlock);
<4>[ 23.431028]
*** DEADLOCK ***
<4>[ 23.431036] May be due to missing lock nesting notation
<4>[ 23.431044] 5 locks held by systemd-udevd/169:
<4>[ 23.431049] #0: (ptrval) (&dev->mutex){....}, at: __driver_attach+0x42/0xe0
<4>[ 23.431065] #1: (ptrval) (&dev->mutex){....}, at: __driver_attach+0x50/0xe0
<4>[ 23.431078] #2: (ptrval) (&dev->struct_mutex){+.+.}, at: i915_gem_init+0xca/0x630 [i915]
<4>[ 23.431174] #3: (ptrval) (rcu_read_lock){....}, at: submit_notify+0x35/0x124 [i915]
<4>[ 23.431271] #4: (ptrval) (&(&timeline->lock)->rlock){....}, at: i915_request_submit+0x1a/0x40 [i915]
<4>[ 23.431369]
stack backtrace:
<4>[ 23.431377] CPU: 0 PID: 169 Comm: systemd-udevd Not tainted 4.17.0-rc4-CI-CI_DRM_4156+ #1
<4>[ 23.431385] Hardware name: Dell Inc. OptiPlex GX280 /0G8310, BIOS A04 02/09/2005
<4>[ 23.431394] Call Trace:
<4>[ 23.431403] dump_stack+0x67/0x9b
...
<4>[ 23.432765] R13: 0000561a47296450 R14: 0000000000020000 R15: 0000561a472a4b30
but did not report it as an issue as it only occurred during the first
module on boot. This is due to the removal of the distinct global
timeline, and its separate lock class. So instead mark up the expected
nesting. An alternative would be to define a separate lock class for the
engine, but since we only expect to have a single point of nesting, we
can avoid having multiple lock classes for the struct.
Fixes: a89d1f921c15 ("drm/i915: Split i915_gem_timeline into individual timelines")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Tested-by: Michel Thierry <michel.thierry@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_request.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index f336942229cf..8928894dd9c7 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -502,7 +502,7 @@ static void move_to_timeline(struct i915_request *request,
GEM_BUG_ON(request->timeline == &request->engine->timeline);
lockdep_assert_held(&request->engine->timeline.lock);
- spin_lock(&request->timeline->lock);
+ spin_lock_nested(&request->timeline->lock, SINGLE_DEPTH_NESTING);
list_move_tail(&request->link, &timeline->requests);
spin_unlock(&request->timeline->lock);
}
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