/**
* \file drm_lock.c
* 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"
static int drm_lock_transfer(drm_device_t * dev,
__volatile__ unsigned int *lock,
unsigned int context);
static int drm_notifier(void *priv);
/**
* Lock ioctl.
*
* \param inode device inode.
* \param filp file pointer.
* \param cmd command.
* \param arg user argument, pointing to a drm_lock structure.
* \return zero on success or negative number on failure.
*
* Add the current task to the lock wait queue, and attempt to take to lock.
*/
int drm_lock(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
{
drm_file_t *priv = filp->private_data;
drm_device_t *dev = priv->head->dev;
DECLARE_WAITQUEUE(entry, current);
drm_lock_t lock;
int ret = 0;
++priv->lock_count;
if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
return -EFAULT;
if (lock.context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
current->pid, lock.context);
return -EINVAL;
}
DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
lock.context, current->pid,
dev->lock.hw_lock->lock, lock.flags);
if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
if (lock.context < 0)
return -EINVAL;
add_wait_queue(&dev->lock.lock_queue, &entry);
for (;;) {
__set_current_state(TASK_INTERRUPTIBLE);
if (!dev->lock.hw_lock) {
/* Device has been unregistered */
ret = -EINTR;
break;
}
if (drm_lock_take(&dev->lock.hw_lock->lock, lock.context)) {
dev->lock.filp = filp;
dev->lock.lock_time = jiffies;
atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
break; /* Got lock */
}
/* Contention */
schedule();
if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
}
__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);
sigaddset(&dev->sigmask, SIGTTIN);
sigaddset(&dev->sigmask, SIGTTOU);
dev->sigdata.context = lock.context;
dev->sigdata.lock = dev->lock.hw_lock;
block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
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)) {
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.
*/
if (dev->driver->kernel_context_switch &&
dev->last_context != lock.context) {
dev->driver->kernel_context_switch(dev, dev->last_context,
lock.context);
}
return 0;
}
/**
* Unlock ioctl.
*
* \param inode device inode.
* \param filp file pointer.
* \param cmd command.
* \param arg user argument, pointing to a drm_lock structure.
* \return zero on success or negative number on failure.
*
* Transfer and free the lock.
*/
int drm_unlock(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
{
drm_file_t *priv = filp->private_data;
drm_device_t *dev = priv->head->dev;
drm_lock_t lock;
if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
return -EFAULT;
if (lock.context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
current->pid, lock.context);
return -EINVAL;
}
atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
/* kernel_context_switch isn't used by any of the x86 drm
* modules but is required by the Sparc driver.
*/
if (dev->driver->kernel_context_switch_unlock)
dev->driver->kernel_context_switch_unlock(dev, &lock);
else {
drm_lock_transfer(dev, &dev->lock.hw_lock->lock,
DRM_KERNEL_CONTEXT);
if (drm_lock_free(dev, &dev->lock.hw_lock->lock,
DRM_KERNEL_CONTEXT)) {
DRM_ERROR("\n");
}
}
unblock_all_signals();
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.
*/
static 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.
*/
static 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;
}
