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/**
* \file drm_lock.h
* IOCTLs for locking
*
* \author Rickard E. (Rik) Faith <faith@valinux.com>
* \author Gareth Hughes <gareth@valinux.com>
*/
/*
* Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com
*
* Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
* Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "drmP.h"
/** No-op ioctl. */
int DRM(noop)(struct inode *inode, struct file *filp, unsigned int cmd,
unsigned long arg)
{
DRM_DEBUG("\n");
return 0;
}
/**
* Take the heavyweight lock.
*
* \param lock lock pointer.
* \param context locking context.
* \return one if the lock is held, or zero otherwise.
*
* Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
*/
int DRM(lock_take)(__volatile__ unsigned int *lock, unsigned int context)
{
unsigned int old, new, prev;
do {
old = *lock;
if (old & _DRM_LOCK_HELD) new = old | _DRM_LOCK_CONT;
else new = context | _DRM_LOCK_HELD;
prev = cmpxchg(lock, old, new);
} while (prev != old);
if (_DRM_LOCKING_CONTEXT(old) == context) {
if (old & _DRM_LOCK_HELD) {
if (context != DRM_KERNEL_CONTEXT) {
DRM_ERROR("%d holds heavyweight lock\n",
context);
}
return 0;
}
}
if (new == (context | _DRM_LOCK_HELD)) {
/* Have lock */
return 1;
}
return 0;
}
/**
* This takes a lock forcibly and hands it to context. Should ONLY be used
* inside *_unlock to give lock to kernel before calling *_dma_schedule.
*
* \param dev DRM device.
* \param lock lock pointer.
* \param context locking context.
* \return always one.
*
* Resets the lock file pointer.
* Marks the lock as held by the given context, via the \p cmpxchg instruction.
*/
int DRM(lock_transfer)(drm_device_t *dev,
__volatile__ unsigned int *lock, unsigned int context)
{
unsigned int old, new, prev;
dev->lock.filp = NULL;
do {
old = *lock;
new = context | _DRM_LOCK_HELD;
prev = cmpxchg(lock, old, new);
} while (prev != old);
return 1;
}
/**
* Free lock.
*
* \param dev DRM device.
* \param lock lock.
* \param context context.
*
* Resets the lock file pointer.
* Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
* waiting on the lock queue.
*/
int DRM(lock_free)(drm_device_t *dev,
__volatile__ unsigned int *lock, unsigned int context)
{
unsigned int old, new, prev;
dev->lock.filp = NULL;
do {
old = *lock;
new = 0;
prev = cmpxchg(lock, old, new);
} while (prev != old);
if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
DRM_ERROR("%d freed heavyweight lock held by %d\n",
context,
_DRM_LOCKING_CONTEXT(old));
return 1;
}
wake_up_interruptible(&dev->lock.lock_queue);
return 0;
}
/**
* If we get here, it means that the process has called DRM_IOCTL_LOCK
* without calling DRM_IOCTL_UNLOCK.
*
* If the lock is not held, then let the signal proceed as usual. If the lock
* is held, then set the contended flag and keep the signal blocked.
*
* \param priv pointer to a drm_sigdata structure.
* \return one if the signal should be delivered normally, or zero if the
* signal should be blocked.
*/
int DRM(notifier)(void *priv)
{
drm_sigdata_t *s = (drm_sigdata_t *)priv;
unsigned int old, new, prev;
/* Allow signal delivery if lock isn't held */
if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
|| _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) return 1;
/* Otherwise, set flag to force call to
drmUnlock */
do {
old = s->lock->lock;
new = old | _DRM_LOCK_CONT;
prev = cmpxchg(&s->lock->lock, old, new);
} while (prev != old);
return 0;
}
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