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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: Dave Airlie <airlied@linux.ie>
This commit is contained in:
Dave Airlie 2005-11-24 21:41:14 +11:00 committed by Dave Airlie
parent 33bc227e4e
commit cf65f1623d
1 changed files with 11 additions and 5 deletions
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16
drivers/char/drm/drm_lock.c
View File

@ -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;
}
/**