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Commit cf65f162 authored by Dave Airlie's avatar Dave Airlie Committed by Dave Airlie
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drm: fix quiescent locking 



A fix for a locking bug which is triggered when a client tries to lock with
flag DMA_QUIESCENT (typically the X server), but gets interrupted by a signal.
The locking IOCTL should then return an error, but if DMA_QUIESCENT succeeds
it returns 0, and the client falsely thinks it has the lock. In addition
The client waits for DMA_QUISCENT and possibly DMA_READY without having the lock.

From: Thomas Hellstrom
Signed-off-by: default avatarDave Airlie <airlied@linux.ie>
parent 33bc227e

drivers/char/drm/drm_lock.c

+11 −5
Original line number Diff line number Diff line
@@ -104,6 +104,10 @@ int drm_lock(struct inode *inode, struct file *filp, 
	__set_current_state(TASK_RUNNING);

	remove_wait_queue(&dev->lock.lock_queue, &entry);



	DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");

	if (ret)

		return ret;



	sigemptyset(&dev->sigmask);

	sigaddset(&dev->sigmask, SIGSTOP);

	sigaddset(&dev->sigmask, SIGTSTP);
@@ -116,8 +120,12 @@ int drm_lock(struct inode *inode, struct file *filp, 
	if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))

		dev->driver->dma_ready(dev);



	if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT))

		return dev->driver->dma_quiescent(dev);

	if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {

		if (dev->driver->dma_quiescent(dev)) {

			DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);

			return DRM_ERR(EBUSY);

		}

	}



	/* dev->driver->kernel_context_switch isn't used by any of the x86

	 *  drivers but is used by the Sparc driver.
@@ -128,9 +136,7 @@ int drm_lock(struct inode *inode, struct file *filp, 
		dev->driver->kernel_context_switch(dev, dev->last_context,

						   lock.context);

	}

	DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");



	return ret;

	return 0;

}



/**