kernel/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         if (timeout == 0)
 163                 return fence_is_signaled(fence);
 164
 165         trace_fence_wait_start(fence);
 166         ret = fence->ops->wait(fence, intr, timeout);
 167         trace_fence_wait_end(fence);
 168         return ret;
 169 }
 170 EXPORT_SYMBOL(fence_wait_timeout);
 171
 172 void fence_release(struct kref *kref)
 173 {
 174         struct fence *fence =
 175                         container_of(kref, struct fence, refcount);
 176
 177         trace_fence_destroy(fence);
 178
 179         BUG_ON(!list_empty(&fence->cb_list));
 180
 181         if (fence->ops->release)
 182                 fence->ops->release(fence);
 183         else
 184                 fence_free(fence);
 185 }
 186 EXPORT_SYMBOL(fence_release);
 187
 188 void fence_free(struct fence *fence)
 189 {
 190         kfree_rcu(fence, rcu);
 191 }
 192 EXPORT_SYMBOL(fence_free);
 193
 194 /**
 195  * fence_enable_sw_signaling - enable signaling on fence
 196  * @fence:      [in]    the fence to enable
 197  *
 198  * this will request for sw signaling to be enabled, to make the fence
 199  * complete as soon as possible
 200  */
 201 void fence_enable_sw_signaling(struct fence *fence)
 202 {
 203         unsigned long flags;
 204
 205         if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&
 206             !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 207                 trace_fence_enable_signal(fence);
 208
 209                 spin_lock_irqsave(fence->lock, flags);
 210
 211                 if (!fence->ops->enable_signaling(fence))
 212                         fence_signal_locked(fence);
 213
 214                 spin_unlock_irqrestore(fence->lock, flags);
 215         }
 216 }
 217 EXPORT_SYMBOL(fence_enable_sw_signaling);
 218
 219 /**
 220  * fence_add_callback - add a callback to be called when the fence
 221  * is signaled
 222  * @fence:      [in]    the fence to wait on
 223  * @cb:         [in]    the callback to register
 224  * @func:       [in]    the function to call
 225  *
 226  * cb will be initialized by fence_add_callback, no initialization
 227  * by the caller is required. Any number of callbacks can be registered
 228  * to a fence, but a callback can only be registered to one fence at a time.
 229  *
 230  * Note that the callback can be called from an atomic context.  If
 231  * fence is already signaled, this function will return -ENOENT (and
 232  * *not* call the callback)
 233  *
 234  * Add a software callback to the fence. Same restrictions apply to
 235  * refcount as it does to fence_wait, however the caller doesn't need to
 236  * keep a refcount to fence afterwards: when software access is enabled,
 237  * the creator of the fence is required to keep the fence alive until
 238  * after it signals with fence_signal. The callback itself can be called
 239  * from irq context.
 240  *
 241  */
 242 int fence_add_callback(struct fence *fence, struct fence_cb *cb,
 243                        fence_func_t func)
 244 {
 245         unsigned long flags;
 246         int ret = 0;
 247         bool was_set;
 248
 249         if (WARN_ON(!fence || !func))
 250                 return -EINVAL;
 251
 252         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
 253                 INIT_LIST_HEAD(&cb->node);
 254                 return -ENOENT;
 255         }
 256
 257         spin_lock_irqsave(fence->lock, flags);
 258
 259         was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
 260
 261         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 262                 ret = -ENOENT;
 263         else if (!was_set) {
 264                 trace_fence_enable_signal(fence);
 265
 266                 if (!fence->ops->enable_signaling(fence)) {
 267                         fence_signal_locked(fence);
 268                         ret = -ENOENT;
 269                 }
 270         }
 271
 272         if (!ret) {
 273                 cb->func = func;
 274                 list_add_tail(&cb->node, &fence->cb_list);
 275         } else
 276                 INIT_LIST_HEAD(&cb->node);
 277         spin_unlock_irqrestore(fence->lock, flags);
 278
 279         return ret;
 280 }
 281 EXPORT_SYMBOL(fence_add_callback);
 282
 283 /**
 284  * fence_remove_callback - remove a callback from the signaling list
 285  * @fence:      [in]    the fence to wait on
 286  * @cb:         [in]    the callback to remove
 287  *
 288  * Remove a previously queued callback from the fence. This function returns
 289  * true if the callback is successfully removed, or false if the fence has
 290  * already been signaled.
 291  *
 292  * *WARNING*:
 293  * Cancelling a callback should only be done if you really know what you're
 294  * doing, since deadlocks and race conditions could occur all too easily. For
 295  * this reason, it should only ever be done on hardware lockup recovery,
 296  * with a reference held to the fence.
 297  */
 298 bool
 299 fence_remove_callback(struct fence *fence, struct fence_cb *cb)
 300 {
 301         unsigned long flags;
 302         bool ret;
 303
 304         spin_lock_irqsave(fence->lock, flags);
 305
 306         ret = !list_empty(&cb->node);
 307         if (ret)
 308                 list_del_init(&cb->node);
 309
 310         spin_unlock_irqrestore(fence->lock, flags);
 311
 312         return ret;
 313 }
 314 EXPORT_SYMBOL(fence_remove_callback);
 315
 316 struct default_wait_cb {
 317         struct fence_cb base;
 318         struct task_struct *task;
 319 };
 320
 321 static void
 322 fence_default_wait_cb(struct fence *fence, struct fence_cb *cb)
 323 {
 324         struct default_wait_cb *wait =
 325                 container_of(cb, struct default_wait_cb, base);
 326
 327         wake_up_state(wait->task, TASK_NORMAL);
 328 }
 329
 330 /**
 331  * fence_default_wait - default sleep until the fence gets signaled
 332  * or until timeout elapses
 333  * @fence:      [in]    the fence to wait on
 334  * @intr:       [in]    if true, do an interruptible wait
 335  * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 336  *
 337  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
 338  * remaining timeout in jiffies on success.
 339  */
 340 signed long
 341 fence_default_wait(struct fence *fence, bool intr, signed long timeout)
 342 {
 343         struct default_wait_cb cb;
 344         unsigned long flags;
 345         signed long ret = timeout;
 346         bool was_set;
 347
 348         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 349                 return timeout;
 350
 351         spin_lock_irqsave(fence->lock, flags);
 352
 353         if (intr && signal_pending(current)) {
 354                 ret = -ERESTARTSYS;
 355                 goto out;
 356         }
 357
 358         was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
 359
 360         if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 361                 goto out;
 362
 363         if (!was_set) {
 364                 trace_fence_enable_signal(fence);
 365
 366                 if (!fence->ops->enable_signaling(fence)) {
 367                         fence_signal_locked(fence);
 368                         goto out;
 369                 }
 370         }
 371
 372         cb.base.func = fence_default_wait_cb;
 373         cb.task = current;
 374         list_add(&cb.base.node, &fence->cb_list);
 375
 376         while (!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
 377                 if (intr)
 378                         __set_current_state(TASK_INTERRUPTIBLE);
 379                 else
 380                         __set_current_state(TASK_UNINTERRUPTIBLE);
 381                 spin_unlock_irqrestore(fence->lock, flags);
 382
 383                 ret = schedule_timeout(ret);
 384
 385                 spin_lock_irqsave(fence->lock, flags);
 386                 if (ret > 0 && intr && signal_pending(current))
 387                         ret = -ERESTARTSYS;
 388         }
 389
 390         if (!list_empty(&cb.base.node))
 391                 list_del(&cb.base.node);
 392         __set_current_state(TASK_RUNNING);
 393
 394 out:
 395         spin_unlock_irqrestore(fence->lock, flags);
 396         return ret;
 397 }
 398 EXPORT_SYMBOL(fence_default_wait);
 399
 400 /**
 401  * fence_init - Initialize a custom fence.
 402  * @fence:      [in]    the fence to initialize
 403  * @ops:        [in]    the fence_ops for operations on this fence
 404  * @lock:       [in]    the irqsafe spinlock to use for locking this fence
 405  * @context:    [in]    the execution context this fence is run on
 406  * @seqno:      [in]    a linear increasing sequence number for this context
 407  *
 408  * Initializes an allocated fence, the caller doesn't have to keep its
 409  * refcount after committing with this fence, but it will need to hold a
 410  * refcount again if fence_ops.enable_signaling gets called. This can
 411  * be used for other implementing other types of fence.
 412  *
 413  * context and seqno are used for easy comparison between fences, allowing
 414  * to check which fence is later by simply using fence_later.
 415  */
 416 void
 417 fence_init(struct fence *fence, const struct fence_ops *ops,
 418              spinlock_t *lock, unsigned context, unsigned seqno)
 419 {
 420         BUG_ON(!lock);
 421         BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
 422                !ops->get_driver_name || !ops->get_timeline_name);
 423
 424         kref_init(&fence->refcount);
 425         fence->ops = ops;
 426         INIT_LIST_HEAD(&fence->cb_list);
 427         fence->lock = lock;
 428         fence->context = context;
 429         fence->seqno = seqno;
 430         fence->flags = 0UL;
 431
 432         trace_fence_init(fence);
 433 }
 434 EXPORT_SYMBOL(fence_init);