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 "drmP.h" 51 52 int 53 drm_lock_take(struct drm_lock_data *lock_data, unsigned int context) 54 { 55 volatile unsigned int *lock = &lock_data->hw_lock->lock; 56 unsigned int old, new; 57 58 do { 59 old = *lock; 60 if (old & _DRM_LOCK_HELD) 61 new = old | _DRM_LOCK_CONT; 62 else 63 new = context | _DRM_LOCK_HELD; 64 } while (!atomic_cmpset_int(lock, old, new)); 65 66 if (_DRM_LOCKING_CONTEXT(old) == context && _DRM_LOCK_IS_HELD(old)) { 67 if (context != DRM_KERNEL_CONTEXT) 68 DRM_ERROR("%d holds heavyweight lock\n", context); 69 return (0); 70 } 71 /* If the lock wasn't held before, it's ours */ 72 return (!_DRM_LOCK_IS_HELD(old)); 73 } 74 75 int 76 drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) 77 { 78 volatile unsigned int *lock = &lock_data->hw_lock->lock; 79 unsigned int old, new; 80 81 mtx_enter(&lock_data->spinlock); 82 lock_data->file_priv = NULL; 83 do { 84 old = *lock; 85 new = 0; 86 } while (!atomic_cmpset_int(lock, old, new)); 87 mtx_leave(&lock_data->spinlock); 88 89 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 90 DRM_ERROR("%d freed heavyweight lock held by %d\n", 91 context, _DRM_LOCKING_CONTEXT(old)); 92 return 1; 93 } 94 wakeup(lock_data); 95 return 0; 96 } 97 98 int 99 drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv) 100 { 101 struct drm_lock *lock = data; 102 int ret = 0; 103 104 if (lock->context == DRM_KERNEL_CONTEXT) { 105 DRM_ERROR("Process %d using kernel context %d\n", 106 DRM_CURRENTPID, lock->context); 107 return EINVAL; 108 } 109 110 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 111 lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock, 112 lock->flags); 113 114 mtx_enter(&dev->lock.spinlock); 115 for (;;) { 116 if (drm_lock_take(&dev->lock, lock->context)) { 117 dev->lock.file_priv = file_priv; 118 break; /* Got lock */ 119 } 120 121 /* Contention */ 122 ret = msleep(&dev->lock, &dev->lock.spinlock, 123 PZERO | PCATCH, "drmlkq", 0); 124 if (ret != 0) 125 break; 126 } 127 mtx_leave(&dev->lock.spinlock); 128 DRM_DEBUG("%d %s\n", lock->context, ret ? "interrupted" : "has lock"); 129 130 if (ret != 0) 131 return ret; 132 133 /* XXX: Add signal blocking here */ 134 135 if (dev->driver->dma_quiescent != NULL && 136 (lock->flags & _DRM_LOCK_QUIESCENT)) 137 dev->driver->dma_quiescent(dev); 138 139 return 0; 140 } 141 142 int 143 drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 144 { 145 struct drm_lock *lock = data; 146 147 if (lock->context == DRM_KERNEL_CONTEXT) { 148 DRM_ERROR("Process %d using kernel context %d\n", 149 DRM_CURRENTPID, lock->context); 150 return EINVAL; 151 } 152 /* Check that the context unlock being requested actually matches 153 * who currently holds the lock. 154 */ 155 if (!_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) || 156 _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock) != lock->context) 157 return EINVAL; 158 159 if (drm_lock_free(&dev->lock, lock->context)) { 160 DRM_ERROR("\n"); 161 } 162 163 return 0; 164 } 165