1 /* $OpenBSD: drm_lock.c,v 1.17 2011/06/02 18:22:00 weerd Exp $ */ 2 /*- 3 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. 4 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. 5 * All Rights Reserved. 6 * 7 * Permission is hereby granted, free of charge, to any person obtaining a 8 * copy of this software and associated documentation files (the "Software"), 9 * to deal in the Software without restriction, including without limitation 10 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 11 * and/or sell copies of the Software, and to permit persons to whom the 12 * Software is furnished to do so, subject to the following conditions: 13 * 14 * The above copyright notice and this permission notice (including the next 15 * paragraph) shall be included in all copies or substantial portions of the 16 * Software. 17 * 18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 21 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 22 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 23 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 24 * OTHER DEALINGS IN THE SOFTWARE. 25 * 26 * Authors: 27 * Rickard E. (Rik) Faith <faith@valinux.com> 28 * Gareth Hughes <gareth@valinux.com> 29 * 30 */ 31 32 /** @file drm_lock.c 33 * Implementation of the ioctls and other support code for dealing with the 34 * hardware lock. 35 * 36 * The DRM hardware lock is a shared structure between the kernel and userland. 37 * 38 * On uncontended access where the new context was the last context, the 39 * client may take the lock without dropping down into the kernel, using atomic 40 * compare-and-set. 41 * 42 * If the client finds during compare-and-set that it was not the last owner 43 * of the lock, it calls the DRM lock ioctl, which may sleep waiting for the 44 * lock, and may have side-effects of kernel-managed context switching. 45 * 46 * When the client releases the lock, if the lock is marked as being contended 47 * by another client, then the DRM unlock ioctl is called so that the 48 * contending client may be woken up. 49 */ 50 51 #include "drmP.h" 52 53 int 54 drm_lock_take(struct drm_lock_data *lock_data, unsigned int context) 55 { 56 volatile unsigned int *lock = &lock_data->hw_lock->lock; 57 unsigned int old, new; 58 59 do { 60 old = *lock; 61 if (old & _DRM_LOCK_HELD) 62 new = old | _DRM_LOCK_CONT; 63 else 64 new = context | _DRM_LOCK_HELD; 65 } while (!atomic_cmpset_int(lock, old, new)); 66 67 if (_DRM_LOCKING_CONTEXT(old) == context && _DRM_LOCK_IS_HELD(old)) { 68 if (context != DRM_KERNEL_CONTEXT) 69 DRM_ERROR("%d holds heavyweight lock\n", context); 70 return (0); 71 } 72 /* If the lock wasn't held before, it's ours */ 73 return (!_DRM_LOCK_IS_HELD(old)); 74 } 75 76 int 77 drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) 78 { 79 volatile unsigned int *lock = &lock_data->hw_lock->lock; 80 unsigned int old, new; 81 82 mtx_enter(&lock_data->spinlock); 83 lock_data->file_priv = NULL; 84 do { 85 old = *lock; 86 new = 0; 87 } while (!atomic_cmpset_int(lock, old, new)); 88 mtx_leave(&lock_data->spinlock); 89 90 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 91 DRM_ERROR("%d freed heavyweight lock held by %d\n", 92 context, _DRM_LOCKING_CONTEXT(old)); 93 return 1; 94 } 95 wakeup(lock_data); 96 return 0; 97 } 98 99 int 100 drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv) 101 { 102 struct drm_lock *lock = data; 103 int ret = 0; 104 105 if (lock->context == DRM_KERNEL_CONTEXT) { 106 DRM_ERROR("Process %d using kernel context %d\n", 107 DRM_CURRENTPID, lock->context); 108 return EINVAL; 109 } 110 111 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 112 lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock, 113 lock->flags); 114 115 mtx_enter(&dev->lock.spinlock); 116 for (;;) { 117 if (drm_lock_take(&dev->lock, lock->context)) { 118 dev->lock.file_priv = file_priv; 119 break; /* Got lock */ 120 } 121 122 /* Contention */ 123 ret = msleep(&dev->lock, &dev->lock.spinlock, 124 PZERO | PCATCH, "drmlkq", 0); 125 if (ret != 0) 126 break; 127 } 128 mtx_leave(&dev->lock.spinlock); 129 DRM_DEBUG("%d %s\n", lock->context, ret ? "interrupted" : "has lock"); 130 131 if (ret != 0) 132 return ret; 133 134 /* XXX: Add signal blocking here */ 135 136 return 0; 137 } 138 139 int 140 drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 141 { 142 struct drm_lock *lock = data; 143 144 if (lock->context == DRM_KERNEL_CONTEXT) { 145 DRM_ERROR("Process %d using kernel context %d\n", 146 DRM_CURRENTPID, lock->context); 147 return EINVAL; 148 } 149 /* Check that the context unlock being requested actually matches 150 * who currently holds the lock. 151 */ 152 if (!_DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) || 153 _DRM_LOCKING_CONTEXT(dev->lock.hw_lock->lock) != lock->context) 154 return EINVAL; 155 156 if (drm_lock_free(&dev->lock, lock->context)) { 157 DRM_ERROR("\n"); 158 } 159 160 return 0; 161 } 162