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Commit ce38f30e authored by Tarun Karra's avatar Tarun Karra
Browse files

msm: kgsl: Prevent deadlock in cmdbatch timer 



Dispatcher can acquire drawctxt->lock if context is pending
and the fence it is waiting on just got signalled.
Dispatcher acquires drawctxt->lock and tries to delete the
cmdbatch timer using delete_timer_sync(). Delete_timer_sync()
waits till timer and its pending handlers are deleted.
But if the timer expires at the same time, timer handler
could be waiting on drawctxt->lock leading to a
deadlock. To prevent this use spin_trylock_bh() instead of
spin_lock_bh(). spin_trylock_bh() does not wait for the lock
if it does not get it and allows the timer handler to finish.
This prevents the deadlock.

Change-Id: Ic2344fed5fccb581b58ec0b66b45ba68af9f1459
Signed-off-by: default avatarTarun Karra <tkarra@codeaurora.org>
parent 7427cd00

drivers/gpu/msm/adreno_drawctxt.c

+15 −1
Original line number Diff line number Diff line
@@ -64,8 +64,22 @@ void adreno_drawctxt_dump(struct kgsl_device *device, 
	 * We may have cmdbatch timer running, which also uses same

	 * lock, take a lock with software interrupt disabled (bh)

	 * to avoid spin lock recursion.

	 *

	 * Use Spin trylock because dispatcher can acquire drawctxt->lock

	 * if context is pending and the fence it is waiting on just got

	 * signalled. Dispatcher acquires drawctxt->lock and tries to

	 * delete the cmdbatch timer using del_timer_sync().

	 * del_timer_sync() waits till timer and its pending handlers

	 * are deleted. But if the timer expires at the same time,

	 * timer handler could be waiting on drawctxt->lock leading to a

	 * deadlock. To prevent this use spin_trylock_bh.

	 */

	spin_lock_bh(&drawctxt->lock);

	if (!spin_trylock_bh(&drawctxt->lock)) {

		dev_err(device->dev, "  context[%d]: could not get lock\n",

			context->id);

		return;

	}



	dev_err(device->dev,

		"  context[%d]: queue=%d, submit=%d, start=%d, retire=%d\n",

		context->id, queue, drawctxt->submitted_timestamp,