/**
* \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 <linux/export.h>
#include <drm/drmP.h>
static int drm_notifier(void *priv);
static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
/**
* Lock ioctl.
*
* \param inode device inode.
* \param file_priv DRM file private.
* \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 drm_device *dev, void *data, struct drm_file *file_priv)
{
DECLARE_WAITQUEUE(entry, current);
struct drm_lock *lock = data;
struct drm_master *master = file_priv->master;
int ret = 0;
++file_priv->lock_count;
if (lock->context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
task_pid_nr(current), lock->context);
return -EINVAL;
}
DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
lock->context, task_pid_nr(current),
master->lock.hw_lock->lock, lock->flags);
add_wait_queue(&master->lock.lock_queue, &entry);
spin_lock_bh(&master->lock.spinlock);
master->lock.user_waiters++;
spin_unlock_bh(&master->lock.spinlock);
for (;;) {
__set_current_state(TASK_INTERRUPTIBLE);
if (!master->lock.hw_lock) {
/* Device has been unregistered */
send_sig(SIGTERM, current, 0);
ret = -EINTR;
break;
}
if (drm_lock_take(&master->lock, lock->context)) {
master->lock.file_priv = file_priv;
master->lock.lock_time = jiffies;
break; /* Got lock */
}
/* Contention */
mutex_unlock(&drm_global_mutex);
schedule();
mutex_lock(&drm_global_mutex);
if (signal_pending(current)) {
ret = -EINTR;
break;
}
}
spin_lock_bh(&master->lock.spinlock);
master->lock.user_waiters--;
spin_unlock_bh(&master->lock.spinlock);
__set_current_state(TASK_RUNNING);
remove_wait_queue(&master->lock.lock_queue, &entry);
DRM_DEBUG("%d %s\n", lock->context,
ret ? "interrupted" : "has lock");
if (ret) return ret;
/* don't set the block all signals on the master process for now
* really probably not the correct answer but lets us debug xkb
* xserver for now */
if (!file_priv->is_master) {
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 = master->lock.hw_lock;
block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
}
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 -EBUSY;
}
}
return 0;
}
/**
* Unlock ioctl.
*
* \param inode device inode.
* \param file_priv DRM file private.
* \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 drm_device *dev, void *data, struct drm_file *file_priv)
{
struct drm_lock *lock = data;
struct drm_master *master = file_priv->master;
if (lock->context == DRM_KERNEL_CONTEXT) {
DRM_ERROR("Process %d using kernel context %d\n",
task_pid_nr(current), lock->context);
return -EINVAL;
}
if (drm_lock_free(&master->lock, lock->context)) {
/* FIXME: Should really bail out here. */
}
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.
*/
static
int drm_lock_take(struct drm_lock_data *lock_data,
unsigned int context)
{
unsigned int old, new, prev;
volatile unsigned int *lock = &lock_data->hw_lock->lock;
spin_lock_bh(&lock_data->spinlock);
do {
old = *lock;
if (old & _DRM_LOCK_HELD)
new = old | _DRM_LOCK_CONT;
else {
new = context | _DRM_LOCK_HELD |
((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
_DRM_LOCK_CONT : 0);
}
prev = cmpxchg(lock, old, new);
} while (prev != old);
spin_unlock_bh(&lock_data->spinlock);
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 ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _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(struct drm_lock_data *lock_data,
unsigned int context)
{
unsigned int old, new, prev;
volatile unsigned int *lock = &lock_data->hw_lock->lock;
lock_data->file_priv = 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(struct drm_lock_data *lock_data, unsigned int context)
{
unsigned int old, new, prev;
volatile unsigned int *lock = &lock_data->hw_lock->lock;
spin_lock_bh(&lock_data->spinlock);
if (lock_data->kernel_waiters != 0) {
drm_lock_transfer(lock_data, 0);
lock_data->idle_has_lock = 1;
spin_unlock_bh(&lock_data->spinlock);
return 1;
}
spin_unlock_bh(&lock_data->spinlock);
do {
old = *lock;
new = _DRM_LOCKING_CONTEXT(old);
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(&lock_data->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)
{
struct drm_sigdata *s = (struct drm_sigdata *) 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;
}
/**
* This function returns immediately and takes the hw lock
* with the kernel context if it is free, otherwise it gets the highest priority when and if
* it is eventually released.
*
* This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
* by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
* a deadlock, which is why the "idlelock" was invented).
*
* This should be sufficient to wait for GPU idle without
* having to worry about starvation.
*/
void drm_idlelock_take(struct drm_lock_data *lock_data)
{
int ret;
spin_lock_bh(&lock_data->spinlock);
lock_data->kernel_waiters++;
if (!lock_data->idle_has_lock) {
spin_unlock_bh(&lock_data->spinlock);
ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
spin_lock_bh(&lock_data->spinlock);
if (ret == 1)
lock_data->idle_has_lock = 1;
}
spin_unlock_bh(&lock_data->spinlock);
}
EXPORT_SYMBOL(drm_idlelock_take);
void drm_idlelock_release(struct drm_lock_data *lock_data)
{
unsigned int old, prev;
volatile unsigned int *lock = &lock_data->hw_lock->lock;
spin_lock_bh(&lock_data->spinlock);
if (--lock_data->kernel_waiters == 0) {
if (lock_data->idle_has_lock) {
do {
old = *lock;
prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
} while (prev != old);
wake_up_interruptible(&lock_data->lock_queue);
lock_data->idle_has_lock = 0;
}
}
spin_unlock_bh(&lock_data->spinlock);
}
EXPORT_SYMBOL(drm_idlelock_release);
int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
{
struct drm_master *master = file_priv->master;
return (file_priv->lock_count && master->lock.hw_lock &&
_DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
master->lock.file_priv == file_priv);
}