/** * \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; }