sys/dev/drm/drm_lock.c

   1 /*-
   2  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
   3  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice (including the next
  14  * paragraph) shall be included in all copies or substantial portions of the
  15  * Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  21  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  22  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  23  * OTHER DEALINGS IN THE SOFTWARE.
  24  *
  25  * Authors:
  26  *    Rickard E. (Rik) Faith <faith@valinux.com>
  27  *    Gareth Hughes <gareth@valinux.com>
  28  *
  29  */
  30
  31 /** @file drm_lock.c
  32  * Implementation of the ioctls and other support code for dealing with the
  33  * hardware lock.
  34  *
  35  * The DRM hardware lock is a shared structure between the kernel and userland.
  36  *
  37  * On uncontended access where the new context was the last context, the
  38  * client may take the lock without dropping down into the kernel, using atomic
  39  * compare-and-set.
  40  *
  41  * If the client finds during compare-and-set that it was not the last owner
  42  * of the lock, it calls the DRM lock ioctl, which may sleep waiting for the
  43  * lock, and may have side-effects of kernel-managed context switching.
  44  *
  45  * When the client releases the lock, if the lock is marked as being contended
  46  * by another client, then the DRM unlock ioctl is called so that the
  47  * contending client may be woken up.
  48  */
  49
  50 #include "dev/drm/drmP.h"
  51
  52 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
  53 {
  54         struct drm_lock *lock = data;
  55         int ret = 0;
  56
  57         if (lock->context == DRM_KERNEL_CONTEXT) {
  58                 DRM_ERROR("Process %d using kernel context %d\n",
  59                     DRM_CURRENTPID, lock->context);
  60                 return EINVAL;
  61         }
  62
  63         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
  64             lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
  65             lock->flags);
  66
  67         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE) &&
  68             lock->context < 0)
  69                 return EINVAL;
  70
  71         DRM_LOCK();
  72         for (;;) {
  73                 if (drm_lock_take(&dev->lock, lock->context)) {
  74                         dev->lock.file_priv = file_priv;
  75                         dev->lock.lock_time = jiffies;
  76                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
  77                         break;  /* Got lock */
  78                 }
  79
  80                 /* Contention */
  81                 tsleep_interlock((void *)&dev->lock.lock_queue, PCATCH);
  82                 DRM_UNLOCK();
  83                 ret = tsleep((void *)&dev->lock.lock_queue,
  84                              PCATCH | PINTERLOCKED, "drmlk2", 0);
  85                 DRM_LOCK();
  86                 if (ret != 0)
  87                         break;
  88         }
  89         DRM_UNLOCK();
  90
  91         if (ret == ERESTART)
  92                 DRM_DEBUG("restarting syscall\n");
  93         else
  94                 DRM_DEBUG("%d %s\n", lock->context,
  95                     ret ? "interrupted" : "has lock");
  96
  97         if (ret != 0)
  98                 return ret;
  99
 100         /* XXX: Add signal blocking here */
 101
 102         if (dev->driver->dma_quiescent != NULL &&
 103             (lock->flags & _DRM_LOCK_QUIESCENT))
 104                 dev->driver->dma_quiescent(dev);
 105
 106         return 0;
 107 }
 108
 109 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 110 {
 111         struct drm_lock *lock = data;
 112
 113         DRM_DEBUG("%d (pid %d) requests unlock (0x%08x), flags = 0x%08x\n",
 114             lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
 115             lock->flags);
 116
 117         if (lock->context == DRM_KERNEL_CONTEXT) {
 118                 DRM_ERROR("Process %d using kernel context %d\n",
 119                     DRM_CURRENTPID, lock->context);
 120                 return EINVAL;
 121         }
 122
 123         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
 124
 125         DRM_LOCK();
 126         drm_lock_transfer(&dev->lock, DRM_KERNEL_CONTEXT);
 127
 128         if (drm_lock_free(&dev->lock, DRM_KERNEL_CONTEXT)) {
 129                 DRM_ERROR("\n");
 130         }
 131         DRM_UNLOCK();
 132
 133         return 0;
 134 }
 135
 136 int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context)
 137 {
 138         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 139         unsigned int old, new;
 140
 141         do {
 142                 old = *lock;
 143                 if (old & _DRM_LOCK_HELD)
 144                         new = old | _DRM_LOCK_CONT;
 145                 else
 146                         new = context | _DRM_LOCK_HELD;
 147         } while (!atomic_cmpset_int(lock, old, new));
 148
 149         if (_DRM_LOCKING_CONTEXT(old) == context) {
 150                 if (old & _DRM_LOCK_HELD) {
 151                         if (context != DRM_KERNEL_CONTEXT) {
 152                                 DRM_ERROR("%d holds heavyweight lock\n",
 153                                     context);
 154                         }
 155                         return 0;
 156                 }
 157         }
 158         if (new == (context | _DRM_LOCK_HELD)) {
 159                 /* Have lock */
 160                 return 1;
 161         }
 162         return 0;
 163 }
 164
 165 /* This takes a lock forcibly and hands it to context.  Should ONLY be used
 166    inside *_unlock to give lock to kernel before calling *_dma_schedule. */
 167 int drm_lock_transfer(struct drm_lock_data *lock_data, unsigned int context)
 168 {
 169         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 170         unsigned int old, new;
 171
 172         lock_data->file_priv = NULL;
 173         do {
 174                 old = *lock;
 175                 new = context | _DRM_LOCK_HELD;
 176         } while (!atomic_cmpset_int(lock, old, new));
 177
 178         return 1;
 179 }
 180
 181 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
 182 {
 183         volatile unsigned int *lock = &lock_data->hw_lock->lock;
 184         unsigned int old, new;
 185
 186         lock_data->file_priv = NULL;
 187         do {
 188                 old = *lock;
 189                 new = 0;
 190         } while (!atomic_cmpset_int(lock, old, new));
 191
 192         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
 193                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
 194                     context, _DRM_LOCKING_CONTEXT(old));
 195                 return 1;
 196         }
 197         DRM_WAKEUP_INT((void *)&lock_data->lock_queue);
 198         return 0;
 199 }