drivers/dma-buf/fence.c

   1 /*
   2  * Fence mechanism for dma-buf and to allow for asynchronous dma access
   3  *
   4  * Copyright (C) 2012 Canonical Ltd
   5  * Copyright (C) 2012 Texas Instruments
   6  *
   7  * Authors:
   8  * Rob Clark <robdclark@gmail.com>
   9  * Maarten Lankhorst <maarten.lankhorst@canonical.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU General Public License version 2 as published by
  13  * the Free Software Foundation.
  14  *
  15  * This program is distributed in the hope that it will be useful, but WITHOUT
  16  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  17  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  18  * more details.
  19  */
  20
  21 #include <linux/slab.h>
  22 #include <linux/export.h>
  23 #include <linux/atomic.h>
  24 #include <linux/fence.h>
  25
  26 #define CREATE_TRACE_POINTS
  27 #include <trace/events/fence.h>
  28
  29 EXPORT_TRACEPOINT_SYMBOL(fence_annotate_wait_on);
  30 EXPORT_TRACEPOINT_SYMBOL(fence_emit);
  31
  32 /*
  33  * fence context counter: each execution context should have its own
  34  * fence context, this allows checking if fences belong to the same
  35  * context or not. One device can have multiple separate contexts,
  36  * and they're used if some engine can run independently of another.
  37  */
  38 static atomic_t fence_context_counter = ATOMIC_INIT(0);
  39
  40 /**
  41  * fence_context_alloc - allocate an array of fence contexts
  42  * @num:        [in]    amount of contexts to allocate
  43  *
  44  * This function will return the first index of the number of fences allocated.
  45  * The fence context is used for setting fence->context to a unique number.
  46  */
  47 unsigned fence_context_alloc(unsigned num)
  48 {
  49         BUG_ON(!num);
  50         return atomic_add_return(num, &fence_context_counter) - num;
  51 }
  52 EXPORT_SYMBOL(fence_context_alloc);
  53
  54 /**
  55  * fence_signal_locked - signal completion of a fence
  56  * @fence: the fence to signal
  57  *
  58  * Signal completion for software callbacks on a fence, this will unblock
  59  * fence_wait() calls and run all the callbacks added with
  60  * fence_add_callback(). Can be called multiple times, but since a fence
  61  * can only go from unsignaled to signaled state, it will only be effective
  62  * the first time.
  63  *
  64  * Unlike fence_signal, this function must be called with fence->lock held.
  65  */
  66 int fence_signal_locked(struct fence *fence)
  67 {
  68         struct fence_cb *cur, *tmp;
  69         int ret = 0;
  70
  71         if (WARN_ON(!fence))
  72                 return -EINVAL;
  73
  74         if (!ktime_to_ns(fence->timestamp)) {
  75                 fence->timestamp = ktime_get();
  76                 smp_mb__before_atomic();
  77         }
  78
  79         if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
  80                 ret = -EINVAL;
  81
  82                 /*
  83                  * we might have raced with the unlocked fence_signal,
  84                  * still run through all callbacks
  85                  */
  86         } else
  87                 trace_fence_signaled(fence);
  88
  89         list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
  90                 list_del_init(&cur->node);
  91                 cur->func(fence, cur);
  92         }
  93         return ret;
  94 }
  95 EXPORT_SYMBOL(fence_signal_locked);
  96
  97 /**
  98  * fence_signal - signal completion of a fence
  99  * @fence: the fence to signal
 100  *
 101  * Signal completion for software callbacks on a fence, this will unblock
 102  * fence_wait() calls and run all the callbacks added with
 103  * fence_add_callback(). Can be called multiple times, but since a fence
 104  * can only go from unsignaled to signaled state, it will only be effective
 105  * the first time.
 106  */
 107 int fence_signal(struct fence *fence)
 108 {
 109         unsigned long flags;
 110
 111         if (!fence)
 112                 return -EINVAL;
 113
 114         if (!ktime_to_ns(fence->timestamp)) {
 115                 fence->timestamp = ktime_get();
 116                 smp_mb__before_atomic();
 117         }
 118
 119         if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 120                 return -EINVAL;
 121
 122         trace_fence_signaled(fence);
 123
 124         if (test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
 125                 struct fence_cb *cur, *tmp;
 126
 127                 spin_lock_irqsave(fence->lock, flags);
 128                 list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
 129                         list_del_init(&cur->node);
 130                         cur->func(fence, cur);
 131                 }
 132                 spin_unlock_irqrestore(fence->lock, flags);
 133         }
 134         return 0;
 135 }
 136 EXPORT_SYMBOL(fence_signal);
 137
 138 /**
 139  * fence_wait_timeout - sleep until the fence gets signaled
 140  * or until timeout elapses
 141  * @fence:      [in]    the fence to wait on
 142  * @intr:       [in]    if true, do an interruptible wait
 143  * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 144  *
 145  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
 146  * remaining timeout in jiffies on success. Other error values may be
 147  * returned on custom implementations.
 148  *
 149  * Performs a synchronous wait on this fence. It is assumed the caller
 150  * directly or indirectly (buf-mgr between reservation and committing)
 151  * holds a reference to the fence, otherwise the fence might be
 152  * freed before return, resulting in undefined behavior.
 153  */
 154 signed long
 155 fence_wait_timeout(struct fence *fence, bool intr, signed long timeout)
 156 {
 157         signed long ret;
 158
 159         if (WARN_ON(timeout < 0))
 160                 return -EINVAL;
 161
 162         trace_fence_wait_start(fence);
 163         ret = fence->ops->wait(fence, intr, timeout);
 164         trace_fence_wait_end(fence);
 165         return ret;
 166 }
 167 EXPORT_SYMBOL(fence_wait_timeout);
 168
 169 void fence_release(struct kref *kref)
 170 {
 171         struct fence *fence =
 172                         container_of(kref, struct fence, refcount);
 173
 174         trace_fence_destroy(fence);
 175
 176         BUG_ON(!list_empty(&fence->cb_list));
 177
 178         if (fence->ops->release)
 179                 fence->ops->release(fence);
 180         else
 181                 fence_free(fence);
 182 }
 183 EXPORT_SYMBOL(fence_release);
 184
 185 void fence_free(struct fence *fence)
 186 {
 187         kfree_rcu(fence, rcu);
 188 }
 189 EXPORT_SYMBOL(fence_free);
 190
 191 /**
 192  * fence_enable_sw_signaling - enable signaling on fence
 193  * @fence:      [in]    the fence to enable
 194  *
 195  * this will request for sw signaling to be enabled, to make the fence
 196  * complete as soon as possible
 197  */
 198 void fence_enable_sw_signaling(struct fence *fence)
 199 {
 200         unsigned long flags;
 201
 202         if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&
 203             !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 204                 trace_fence_enable_signal(fence);
 205
 206                 spin_lock_irqsave(fence->lock, flags);
 207
 208                 if (!fence->ops->enable_signaling(fence))
 209                         fence_signal_locked(fence);
 210
 211                 spin_unlock_irqrestore(fence->lock, flags);
 212         }
 213 }
 214 EXPORT_SYMBOL(fence_enable_sw_signaling);
 215
 216 /**
 217  * fence_add_callback - add a callback to be called when the fence
 218  * is signaled
 219  * @fence:      [in]    the fence to wait on
 220  * @cb:         [in]    the callback to register
 221  * @func:       [in]    the function to call
 222  *
 223  * cb will be initialized by fence_add_callback, no initialization
 224  * by the caller is required. Any number of callbacks can be registered
 225  * to a fence, but a callback can only be registered to one fence at a time.
 226  *
 227  * Note that the callback can be called from an atomic context.  If
 228  * fence is already signaled, this function will return -ENOENT (and
 229  * *not* call the callback)
 230  *
 231  * Add a software callback to the fence. Same restrictions apply to
 232  * refcount as it does to fence_wait, however the caller doesn't need to
 233  * keep a refcount to fence afterwards: when software access is enabled,
 234  * the creator of the fence is required to keep the fence alive until
 235  * after it signals with fence_signal. The callback itself can be called
 236  * from irq context.
 237  *
 238  */
 239 int fence_add_callback(struct fence *fence, struct fence_cb *cb,
 240                        fence_func_t func)
 241 {
 242         unsigned long flags;
 243         int ret = 0;
 244         bool was_set;
 245
 246         if (WARN_ON(!fence || !func))
 247                 return -EINVAL;
 248
 249         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 250                 INIT_LIST_HEAD(&cb->node);
 251                 return -ENOENT;
 252         }
 253
 254         spin_lock_irqsave(fence->lock, flags);
 255
 256         was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
 257
 258         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 259                 ret = -ENOENT;
 260         else if (!was_set) {
 261                 trace_fence_enable_signal(fence);
 262
 263                 if (!fence->ops->enable_signaling(fence)) {
 264                         fence_signal_locked(fence);
 265                         ret = -ENOENT;
 266                 }
 267         }
 268
 269         if (!ret) {
 270                 cb->func = func;
 271                 list_add_tail(&cb->node, &fence->cb_list);
 272         } else
 273                 INIT_LIST_HEAD(&cb->node);
 274         spin_unlock_irqrestore(fence->lock, flags);
 275
 276         return ret;
 277 }
 278 EXPORT_SYMBOL(fence_add_callback);
 279
 280 /**
 281  * fence_remove_callback - remove a callback from the signaling list
 282  * @fence:      [in]    the fence to wait on
 283  * @cb:         [in]    the callback to remove
 284  *
 285  * Remove a previously queued callback from the fence. This function returns
 286  * true if the callback is succesfully removed, or false if the fence has
 287  * already been signaled.
 288  *
 289  * *WARNING*:
 290  * Cancelling a callback should only be done if you really know what you're
 291  * doing, since deadlocks and race conditions could occur all too easily. For
 292  * this reason, it should only ever be done on hardware lockup recovery,
 293  * with a reference held to the fence.
 294  */
 295 bool
 296 fence_remove_callback(struct fence *fence, struct fence_cb *cb)
 297 {
 298         unsigned long flags;
 299         bool ret;
 300
 301         spin_lock_irqsave(fence->lock, flags);
 302
 303         ret = !list_empty(&cb->node);
 304         if (ret)
 305                 list_del_init(&cb->node);
 306
 307         spin_unlock_irqrestore(fence->lock, flags);
 308
 309         return ret;
 310 }
 311 EXPORT_SYMBOL(fence_remove_callback);
 312
 313 struct default_wait_cb {
 314         struct fence_cb base;
 315         struct task_struct *task;
 316 };
 317
 318 static void
 319 fence_default_wait_cb(struct fence *fence, struct fence_cb *cb)
 320 {
 321         struct default_wait_cb *wait =
 322                 container_of(cb, struct default_wait_cb, base);
 323
 324         wake_up_state(wait->task, TASK_NORMAL);
 325 }
 326
 327 /**
 328  * fence_default_wait - default sleep until the fence gets signaled
 329  * or until timeout elapses
 330  * @fence:      [in]    the fence to wait on
 331  * @intr:       [in]    if true, do an interruptible wait
 332  * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 333  *
 334  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
 335  * remaining timeout in jiffies on success.
 336  */
 337 signed long
 338 fence_default_wait(struct fence *fence, bool intr, signed long timeout)
 339 {
 340         struct default_wait_cb cb;
 341         unsigned long flags;
 342         signed long ret = timeout;
 343         bool was_set;
 344
 345         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 346                 return timeout;
 347
 348         spin_lock_irqsave(fence->lock, flags);
 349
 350         if (intr && signal_pending(current)) {
 351                 ret = -ERESTARTSYS;
 352                 goto out;
 353         }
 354
 355         was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
 356
 357         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 358                 goto out;
 359
 360         if (!was_set) {
 361                 trace_fence_enable_signal(fence);
 362
 363                 if (!fence->ops->enable_signaling(fence)) {
 364                         fence_signal_locked(fence);
 365                         goto out;
 366                 }
 367         }
 368
 369         cb.base.func = fence_default_wait_cb;
 370         cb.task = current;
 371         list_add(&cb.base.node, &fence->cb_list);
 372
 373         while (!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
 374                 if (intr)
 375                         __set_current_state(TASK_INTERRUPTIBLE);
 376                 else
 377                         __set_current_state(TASK_UNINTERRUPTIBLE);
 378                 spin_unlock_irqrestore(fence->lock, flags);
 379
 380                 ret = schedule_timeout(ret);
 381
 382                 spin_lock_irqsave(fence->lock, flags);
 383                 if (ret > 0 && intr && signal_pending(current))
 384                         ret = -ERESTARTSYS;
 385         }
 386
 387         if (!list_empty(&cb.base.node))
 388                 list_del(&cb.base.node);
 389         __set_current_state(TASK_RUNNING);
 390
 391 out:
 392         spin_unlock_irqrestore(fence->lock, flags);
 393         return ret;
 394 }
 395 EXPORT_SYMBOL(fence_default_wait);
 396
 397 /**
 398  * fence_init - Initialize a custom fence.
 399  * @fence:      [in]    the fence to initialize
 400  * @ops:        [in]    the fence_ops for operations on this fence
 401  * @lock:       [in]    the irqsafe spinlock to use for locking this fence
 402  * @context:    [in]    the execution context this fence is run on
 403  * @seqno:      [in]    a linear increasing sequence number for this context
 404  *
 405  * Initializes an allocated fence, the caller doesn't have to keep its
 406  * refcount after committing with this fence, but it will need to hold a
 407  * refcount again if fence_ops.enable_signaling gets called. This can
 408  * be used for other implementing other types of fence.
 409  *
 410  * context and seqno are used for easy comparison between fences, allowing
 411  * to check which fence is later by simply using fence_later.
 412  */
 413 void
 414 fence_init(struct fence *fence, const struct fence_ops *ops,
 415              spinlock_t *lock, unsigned context, unsigned seqno)
 416 {
 417         BUG_ON(!lock);
 418         BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
 419                !ops->get_driver_name || !ops->get_timeline_name);
 420
 421         kref_init(&fence->refcount);
 422         fence->ops = ops;
 423         INIT_LIST_HEAD(&fence->cb_list);
 424         fence->lock = lock;
 425         fence->context = context;
 426         fence->seqno = seqno;
 427         fence->flags = 0UL;
 428
 429         trace_fence_init(fence);
 430 }
 431 EXPORT_SYMBOL(fence_init);