Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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>
authored by Dave Airlie and committed by Dave Airlie cf65f162 33bc227e
+11
-5
drivers/char/drm/drm_lock.c
+11
-5
drivers/char/drm/drm_lock.c
···
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__set_current_state(TASK_RUNNING);
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remove_wait_queue(&dev->lock.lock_queue, &entry);
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+
DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
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+
if (ret)
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+
return ret;
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+
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sigemptyset(&dev->sigmask);
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sigaddset(&dev->sigmask, SIGSTOP);
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sigaddset(&dev->sigmask, SIGTSTP);
···
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if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
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dev->driver->dma_ready(dev);
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-
if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT))
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-
return dev->driver->dma_quiescent(dev);
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+
if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT)) {
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if (dev->driver->dma_quiescent(dev)) {
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+
DRM_DEBUG("%d waiting for DMA quiescent\n", lock.context);
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return DRM_ERR(EBUSY);
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+
}
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+
}
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/* dev->driver->kernel_context_switch isn't used by any of the x86
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* drivers but is used by the Sparc driver.
···
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dev->driver->kernel_context_switch(dev, dev->last_context,
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lock.context);
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}
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-
DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
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-
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-
return ret;
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+
return 0;
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}
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/**