include/drm/ttm/ttm_lock.h

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  27 /*
  28  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  29  */
  30
  31 /** @file ttm_lock.h
  32  * This file implements a simple replacement for the buffer manager use
  33  * of the DRM heavyweight hardware lock.
  34  * The lock is a read-write lock. Taking it in read mode and write mode
  35  * is relatively fast, and intended for in-kernel use only.
  36  *
  37  * The vt mode is used only when there is a need to block all
  38  * user-space processes from validating buffers.
  39  * It's allowed to leave kernel space with the vt lock held.
  40  * If a user-space process dies while having the vt-lock,
  41  * it will be released during the file descriptor release. The vt lock
  42  * excludes write lock and read lock.
  43  *
  44  * The suspend mode is used to lock out all TTM users when preparing for
  45  * and executing suspend operations.
  46  *
  47  */
  48
  49 #ifndef _TTM_LOCK_H_
  50 #define _TTM_LOCK_H_
  51
  52 #include <ttm/ttm_object.h>
  53 #include <linux/wait.h>
  54 #include <linux/atomic.h>
  55
  56 /**
  57  * struct ttm_lock
  58  *
  59  * @base: ttm base object used solely to release the lock if the client
  60  * holding the lock dies.
  61  * @queue: Queue for processes waiting for lock change-of-status.
  62  * @lock: Spinlock protecting some lock members.
  63  * @rw: Read-write lock counter. Protected by @lock.
  64  * @flags: Lock state. Protected by @lock.
  65  * @kill_takers: Boolean whether to kill takers of the lock.
  66  * @signal: Signal to send when kill_takers is true.
  67  */
  68
  69 struct ttm_lock {
  70         struct ttm_base_object base;
  71         wait_queue_head_t queue;
  72         spinlock_t lock;
  73         int32_t rw;
  74         uint32_t flags;
  75         bool kill_takers;
  76         int signal;
  77         struct ttm_object_file *vt_holder;
  78 };
  79
  80
  81 /**
  82  * ttm_lock_init
  83  *
  84  * @lock: Pointer to a struct ttm_lock
  85  * Initializes the lock.
  86  */
  87 extern void ttm_lock_init(struct ttm_lock *lock);
  88
  89 /**
  90  * ttm_read_unlock
  91  *
  92  * @lock: Pointer to a struct ttm_lock
  93  *
  94  * Releases a read lock.
  95  */
  96 extern void ttm_read_unlock(struct ttm_lock *lock);
  97
  98 /**
  99  * ttm_read_lock
 100  *
 101  * @lock: Pointer to a struct ttm_lock
 102  * @interruptible: Interruptible sleeping while waiting for a lock.
 103  *
 104  * Takes the lock in read mode.
 105  * Returns:
 106  * -ERESTARTSYS If interrupted by a signal and interruptible is true.
 107  */
 108 extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible);
 109
 110 /**
 111  * ttm_read_trylock
 112  *
 113  * @lock: Pointer to a struct ttm_lock
 114  * @interruptible: Interruptible sleeping while waiting for a lock.
 115  *
 116  * Tries to take the lock in read mode. If the lock is already held
 117  * in write mode, the function will return -EBUSY. If the lock is held
 118  * in vt or suspend mode, the function will sleep until these modes
 119  * are unlocked.
 120  *
 121  * Returns:
 122  * -EBUSY The lock was already held in write mode.
 123  * -ERESTARTSYS If interrupted by a signal and interruptible is true.
 124  */
 125 extern int ttm_read_trylock(struct ttm_lock *lock, bool interruptible);
 126
 127 /**
 128  * ttm_write_unlock
 129  *
 130  * @lock: Pointer to a struct ttm_lock
 131  *
 132  * Releases a write lock.
 133  */
 134 extern void ttm_write_unlock(struct ttm_lock *lock);
 135
 136 /**
 137  * ttm_write_lock
 138  *
 139  * @lock: Pointer to a struct ttm_lock
 140  * @interruptible: Interruptible sleeping while waiting for a lock.
 141  *
 142  * Takes the lock in write mode.
 143  * Returns:
 144  * -ERESTARTSYS If interrupted by a signal and interruptible is true.
 145  */
 146 extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
 147
 148 /**
 149  * ttm_lock_downgrade
 150  *
 151  * @lock: Pointer to a struct ttm_lock
 152  *
 153  * Downgrades a write lock to a read lock.
 154  */
 155 extern void ttm_lock_downgrade(struct ttm_lock *lock);
 156
 157 /**
 158  * ttm_suspend_lock
 159  *
 160  * @lock: Pointer to a struct ttm_lock
 161  *
 162  * Takes the lock in suspend mode. Excludes read and write mode.
 163  */
 164 extern void ttm_suspend_lock(struct ttm_lock *lock);
 165
 166 /**
 167  * ttm_suspend_unlock
 168  *
 169  * @lock: Pointer to a struct ttm_lock
 170  *
 171  * Releases a suspend lock
 172  */
 173 extern void ttm_suspend_unlock(struct ttm_lock *lock);
 174
 175 /**
 176  * ttm_vt_lock
 177  *
 178  * @lock: Pointer to a struct ttm_lock
 179  * @interruptible: Interruptible sleeping while waiting for a lock.
 180  * @tfile: Pointer to a struct ttm_object_file to register the lock with.
 181  *
 182  * Takes the lock in vt mode.
 183  * Returns:
 184  * -ERESTARTSYS If interrupted by a signal and interruptible is true.
 185  * -ENOMEM: Out of memory when locking.
 186  */
 187 extern int ttm_vt_lock(struct ttm_lock *lock, bool interruptible,
 188                        struct ttm_object_file *tfile);
 189
 190 /**
 191  * ttm_vt_unlock
 192  *
 193  * @lock: Pointer to a struct ttm_lock
 194  *
 195  * Releases a vt lock.
 196  * Returns:
 197  * -EINVAL If the lock was not held.
 198  */
 199 extern int ttm_vt_unlock(struct ttm_lock *lock);
 200
 201 /**
 202  * ttm_write_unlock
 203  *
 204  * @lock: Pointer to a struct ttm_lock
 205  *
 206  * Releases a write lock.
 207  */
 208 extern void ttm_write_unlock(struct ttm_lock *lock);
 209
 210 /**
 211  * ttm_write_lock
 212  *
 213  * @lock: Pointer to a struct ttm_lock
 214  * @interruptible: Interruptible sleeping while waiting for a lock.
 215  *
 216  * Takes the lock in write mode.
 217  * Returns:
 218  * -ERESTARTSYS If interrupted by a signal and interruptible is true.
 219  */
 220 extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
 221
 222 /**
 223  * ttm_lock_set_kill
 224  *
 225  * @lock: Pointer to a struct ttm_lock
 226  * @val: Boolean whether to kill processes taking the lock.
 227  * @signal: Signal to send to the process taking the lock.
 228  *
 229  * The kill-when-taking-lock functionality is used to kill processes that keep
 230  * on using the TTM functionality when its resources has been taken down, for
 231  * example when the X server exits. A typical sequence would look like this:
 232  * - X server takes lock in write mode.
 233  * - ttm_lock_set_kill() is called with @val set to true.
 234  * - As part of X server exit, TTM resources are taken down.
 235  * - X server releases the lock on file release.
 236  * - Another dri client wants to render, takes the lock and is killed.
 237  *
 238  */
 239 static inline void ttm_lock_set_kill(struct ttm_lock *lock, bool val,
 240                                      int signal)
 241 {
 242         lock->kill_takers = val;
 243         if (val)
 244                 lock->signal = signal;
 245 }
 246
 247 #endif