// SPDX-License-Identifier: GPL-2.0-only /* * Fence mechanism for dma-buf and to allow for asynchronous dma access * * Copyright (C) 2012 Canonical Ltd * Copyright (C) 2012 Texas Instruments * * Authors: * Rob Clark * Maarten Lankhorst */ #include #include #include #include #include #define CREATE_TRACE_POINTS #include EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit); EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal); EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled); static DEFINE_SPINLOCK(dma_fence_stub_lock); static struct dma_fence dma_fence_stub; /* * fence context counter: each execution context should have its own * fence context, this allows checking if fences belong to the same * context or not. One device can have multiple separate contexts, * and they're used if some engine can run independently of another. */ static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1); /** * DOC: DMA fences overview * * DMA fences, represented by &struct dma_fence, are the kernel internal * synchronization primitive for DMA operations like GPU rendering, video * encoding/decoding, or displaying buffers on a screen. * * A fence is initialized using dma_fence_init() and completed using * dma_fence_signal(). Fences are associated with a context, allocated through * dma_fence_context_alloc(), and all fences on the same context are * fully ordered. * * Since the purposes of fences is to facilitate cross-device and * cross-application synchronization, there's multiple ways to use one: * * - Individual fences can be exposed as a &sync_file, accessed as a file * descriptor from userspace, created by calling sync_file_create(). This is * called explicit fencing, since userspace passes around explicit * synchronization points. * * - Some subsystems also have their own explicit fencing primitives, like * &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying * fence to be updated. * * - Then there's also implicit fencing, where the synchronization points are * implicitly passed around as part of shared &dma_buf instances. Such * implicit fences are stored in &struct dma_resv through the * &dma_buf.resv pointer. */ static const char *dma_fence_stub_get_name(struct dma_fence *fence) { return "stub"; } static const struct dma_fence_ops dma_fence_stub_ops = { .get_driver_name = dma_fence_stub_get_name, .get_timeline_name = dma_fence_stub_get_name, }; /** * dma_fence_get_stub - return a signaled fence * * Return a stub fence which is already signaled. */ struct dma_fence *dma_fence_get_stub(void) { spin_lock(&dma_fence_stub_lock); if (!dma_fence_stub.ops) { dma_fence_init(&dma_fence_stub, &dma_fence_stub_ops, &dma_fence_stub_lock, 0, 0); dma_fence_signal_locked(&dma_fence_stub); } spin_unlock(&dma_fence_stub_lock); return dma_fence_get(&dma_fence_stub); } EXPORT_SYMBOL(dma_fence_get_stub); /** * dma_fence_context_alloc - allocate an array of fence contexts * @num: amount of contexts to allocate * * This function will return the first index of the number of fence contexts * allocated. The fence context is used for setting &dma_fence.context to a * unique number by passing the context to dma_fence_init(). */ u64 dma_fence_context_alloc(unsigned num) { WARN_ON(!num); return atomic64_fetch_add(num, &dma_fence_context_counter); } EXPORT_SYMBOL(dma_fence_context_alloc); /** * dma_fence_signal_locked - signal completion of a fence * @fence: the fence to signal * * Signal completion for software callbacks on a fence, this will unblock * dma_fence_wait() calls and run all the callbacks added with * dma_fence_add_callback(). Can be called multiple times, but since a fence * can only go from the unsignaled to the signaled state and not back, it will * only be effective the first time. * * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock * held. * * Returns 0 on success and a negative error value when @fence has been * signalled already. */ int dma_fence_signal_locked(struct dma_fence *fence) { struct dma_fence_cb *cur, *tmp; struct list_head cb_list; lockdep_assert_held(fence->lock); if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))) return -EINVAL; /* Stash the cb_list before replacing it with the timestamp */ list_replace(&fence->cb_list, &cb_list); fence->timestamp = ktime_get(); set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags); trace_dma_fence_signaled(fence); list_for_each_entry_safe(cur, tmp, &cb_list, node) { INIT_LIST_HEAD(&cur->node); cur->func(fence, cur); } return 0; } EXPORT_SYMBOL(dma_fence_signal_locked); /** * dma_fence_signal - signal completion of a fence * @fence: the fence to signal * * Signal completion for software callbacks on a fence, this will unblock * dma_fence_wait() calls and run all the callbacks added with * dma_fence_add_callback(). Can be called multiple times, but since a fence * can only go from the unsignaled to the signaled state and not back, it will * only be effective the first time. * * Returns 0 on success and a negative error value when @fence has been * signalled already. */ int dma_fence_signal(struct dma_fence *fence) { unsigned long flags; int ret; if (!fence) return -EINVAL; spin_lock_irqsave(fence->lock, flags); ret = dma_fence_signal_locked(fence); spin_unlock_irqrestore(fence->lock, flags); return ret; } EXPORT_SYMBOL(dma_fence_signal); /** * dma_fence_wait_timeout - sleep until the fence gets signaled * or until timeout elapses * @fence: the fence to wait on * @intr: if true, do an interruptible wait * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT * * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the * remaining timeout in jiffies on success. Other error values may be * returned on custom implementations. * * Performs a synchronous wait on this fence. It is assumed the caller * directly or indirectly (buf-mgr between reservation and committing) * holds a reference to the fence, otherwise the fence might be * freed before return, resulting in undefined behavior. * * See also dma_fence_wait() and dma_fence_wait_any_timeout(). */ signed long dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout) { signed long ret; if (WARN_ON(timeout < 0)) return -EINVAL; might_sleep(); trace_dma_fence_wait_start(fence); if (fence->ops->wait) ret = fence->ops->wait(fence, intr, timeout); else ret = dma_fence_default_wait(fence, intr, timeout); trace_dma_fence_wait_end(fence); return ret; } EXPORT_SYMBOL(dma_fence_wait_timeout); /** * dma_fence_release - default relese function for fences * @kref: &dma_fence.recfount * * This is the default release functions for &dma_fence. Drivers shouldn't call * this directly, but instead call dma_fence_put(). */ void dma_fence_release(struct kref *kref) { struct dma_fence *fence = container_of(kref, struct dma_fence, refcount); trace_dma_fence_destroy(fence); if (WARN(!list_empty(&fence->cb_list) && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags), "Fence %s:%s:%llx:%llx released with pending signals!\n", fence->ops->get_driver_name(fence), fence->ops->get_timeline_name(fence), fence->context, fence->seqno)) { unsigned long flags; /* * Failed to signal before release, likely a refcounting issue. * * This should never happen, but if it does make sure that we * don't leave chains dangling. We set the error flag first * so that the callbacks know this signal is due to an error. */ spin_lock_irqsave(fence->lock, flags); fence->error = -EDEADLK; dma_fence_signal_locked(fence); spin_unlock_irqrestore(fence->lock, flags); } if (fence->ops->release) fence->ops->release(fence); else dma_fence_free(fence); } EXPORT_SYMBOL(dma_fence_release); /** * dma_fence_free - default release function for &dma_fence. * @fence: fence to release * * This is the default implementation for &dma_fence_ops.release. It calls * kfree_rcu() on @fence. */ void dma_fence_free(struct dma_fence *fence) { kfree_rcu(fence, rcu); } EXPORT_SYMBOL(dma_fence_free); static bool __dma_fence_enable_signaling(struct dma_fence *fence) { bool was_set; lockdep_assert_held(fence->lock); was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags); if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return false; if (!was_set && fence->ops->enable_signaling) { trace_dma_fence_enable_signal(fence); if (!fence->ops->enable_signaling(fence)) { dma_fence_signal_locked(fence); return false; } } return true; } /** * dma_fence_enable_sw_signaling - enable signaling on fence * @fence: the fence to enable * * This will request for sw signaling to be enabled, to make the fence * complete as soon as possible. This calls &dma_fence_ops.enable_signaling * internally. */ void dma_fence_enable_sw_signaling(struct dma_fence *fence) { unsigned long flags; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return; spin_lock_irqsave(fence->lock, flags); __dma_fence_enable_signaling(fence); spin_unlock_irqrestore(fence->lock, flags); } EXPORT_SYMBOL(dma_fence_enable_sw_signaling); /** * dma_fence_add_callback - add a callback to be called when the fence * is signaled * @fence: the fence to wait on * @cb: the callback to register * @func: the function to call * * @cb will be initialized by dma_fence_add_callback(), no initialization * by the caller is required. Any number of callbacks can be registered * to a fence, but a callback can only be registered to one fence at a time. * * Note that the callback can be called from an atomic context. If * fence is already signaled, this function will return -ENOENT (and * *not* call the callback). * * Add a software callback to the fence. Same restrictions apply to * refcount as it does to dma_fence_wait(), however the caller doesn't need to * keep a refcount to fence afterward dma_fence_add_callback() has returned: * when software access is enabled, the creator of the fence is required to keep * the fence alive until after it signals with dma_fence_signal(). The callback * itself can be called from irq context. * * Returns 0 in case of success, -ENOENT if the fence is already signaled * and -EINVAL in case of error. */ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb, dma_fence_func_t func) { unsigned long flags; int ret = 0; if (WARN_ON(!fence || !func)) return -EINVAL; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { INIT_LIST_HEAD(&cb->node); return -ENOENT; } spin_lock_irqsave(fence->lock, flags); if (__dma_fence_enable_signaling(fence)) { cb->func = func; list_add_tail(&cb->node, &fence->cb_list); } else { INIT_LIST_HEAD(&cb->node); ret = -ENOENT; } spin_unlock_irqrestore(fence->lock, flags); return ret; } EXPORT_SYMBOL(dma_fence_add_callback); /** * dma_fence_get_status - returns the status upon completion * @fence: the dma_fence to query * * This wraps dma_fence_get_status_locked() to return the error status * condition on a signaled fence. See dma_fence_get_status_locked() for more * details. * * Returns 0 if the fence has not yet been signaled, 1 if the fence has * been signaled without an error condition, or a negative error code * if the fence has been completed in err. */ int dma_fence_get_status(struct dma_fence *fence) { unsigned long flags; int status; spin_lock_irqsave(fence->lock, flags); status = dma_fence_get_status_locked(fence); spin_unlock_irqrestore(fence->lock, flags); return status; } EXPORT_SYMBOL(dma_fence_get_status); /** * dma_fence_remove_callback - remove a callback from the signaling list * @fence: the fence to wait on * @cb: the callback to remove * * Remove a previously queued callback from the fence. This function returns * true if the callback is successfully removed, or false if the fence has * already been signaled. * * *WARNING*: * Cancelling a callback should only be done if you really know what you're * doing, since deadlocks and race conditions could occur all too easily. For * this reason, it should only ever be done on hardware lockup recovery, * with a reference held to the fence. * * Behaviour is undefined if @cb has not been added to @fence using * dma_fence_add_callback() beforehand. */ bool dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb) { unsigned long flags; bool ret; spin_lock_irqsave(fence->lock, flags); ret = !list_empty(&cb->node); if (ret) list_del_init(&cb->node); spin_unlock_irqrestore(fence->lock, flags); return ret; } EXPORT_SYMBOL(dma_fence_remove_callback); struct default_wait_cb { struct dma_fence_cb base; struct task_struct *task; }; static void dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb) { struct default_wait_cb *wait = container_of(cb, struct default_wait_cb, base); wake_up_state(wait->task, TASK_NORMAL); } /** * dma_fence_default_wait - default sleep until the fence gets signaled * or until timeout elapses * @fence: the fence to wait on * @intr: if true, do an interruptible wait * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT * * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the * remaining timeout in jiffies on success. If timeout is zero the value one is * returned if the fence is already signaled for consistency with other * functions taking a jiffies timeout. */ signed long dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout) { struct default_wait_cb cb; unsigned long flags; signed long ret = timeout ? timeout : 1; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return ret; spin_lock_irqsave(fence->lock, flags); if (intr && signal_pending(current)) { ret = -ERESTARTSYS; goto out; } if (!__dma_fence_enable_signaling(fence)) goto out; if (!timeout) { ret = 0; goto out; } cb.base.func = dma_fence_default_wait_cb; cb.task = current; list_add(&cb.base.node, &fence->cb_list); while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) { if (intr) __set_current_state(TASK_INTERRUPTIBLE); else __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock_irqrestore(fence->lock, flags); ret = schedule_timeout(ret); spin_lock_irqsave(fence->lock, flags); if (ret > 0 && intr && signal_pending(current)) ret = -ERESTARTSYS; } if (!list_empty(&cb.base.node)) list_del(&cb.base.node); __set_current_state(TASK_RUNNING); out: spin_unlock_irqrestore(fence->lock, flags); return ret; } EXPORT_SYMBOL(dma_fence_default_wait); static bool dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count, uint32_t *idx) { int i; for (i = 0; i < count; ++i) { struct dma_fence *fence = fences[i]; if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { if (idx) *idx = i; return true; } } return false; } /** * dma_fence_wait_any_timeout - sleep until any fence gets signaled * or until timeout elapses * @fences: array of fences to wait on * @count: number of fences to wait on * @intr: if true, do an interruptible wait * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT * @idx: used to store the first signaled fence index, meaningful only on * positive return * * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies * on success. * * Synchronous waits for the first fence in the array to be signaled. The * caller needs to hold a reference to all fences in the array, otherwise a * fence might be freed before return, resulting in undefined behavior. * * See also dma_fence_wait() and dma_fence_wait_timeout(). */ signed long dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, bool intr, signed long timeout, uint32_t *idx) { struct default_wait_cb *cb; signed long ret = timeout; unsigned i; if (WARN_ON(!fences || !count || timeout < 0)) return -EINVAL; if (timeout == 0) { for (i = 0; i < count; ++i) if (dma_fence_is_signaled(fences[i])) { if (idx) *idx = i; return 1; } return 0; } cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL); if (cb == NULL) { ret = -ENOMEM; goto err_free_cb; } for (i = 0; i < count; ++i) { struct dma_fence *fence = fences[i]; cb[i].task = current; if (dma_fence_add_callback(fence, &cb[i].base, dma_fence_default_wait_cb)) { /* This fence is already signaled */ if (idx) *idx = i; goto fence_rm_cb; } } while (ret > 0) { if (intr) set_current_state(TASK_INTERRUPTIBLE); else set_current_state(TASK_UNINTERRUPTIBLE); if (dma_fence_test_signaled_any(fences, count, idx)) break; ret = schedule_timeout(ret); if (ret > 0 && intr && signal_pending(current)) ret = -ERESTARTSYS; } __set_current_state(TASK_RUNNING); fence_rm_cb: while (i-- > 0) dma_fence_remove_callback(fences[i], &cb[i].base); err_free_cb: kfree(cb); return ret; } EXPORT_SYMBOL(dma_fence_wait_any_timeout); /** * dma_fence_init - Initialize a custom fence. * @fence: the fence to initialize * @ops: the dma_fence_ops for operations on this fence * @lock: the irqsafe spinlock to use for locking this fence * @context: the execution context this fence is run on * @seqno: a linear increasing sequence number for this context * * Initializes an allocated fence, the caller doesn't have to keep its * refcount after committing with this fence, but it will need to hold a * refcount again if &dma_fence_ops.enable_signaling gets called. * * context and seqno are used for easy comparison between fences, allowing * to check which fence is later by simply using dma_fence_later(). */ void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops, spinlock_t *lock, u64 context, u64 seqno) { BUG_ON(!lock); BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name); kref_init(&fence->refcount); fence->ops = ops; INIT_LIST_HEAD(&fence->cb_list); fence->lock = lock; fence->context = context; fence->seqno = seqno; fence->flags = 0UL; fence->error = 0; trace_dma_fence_init(fence); } EXPORT_SYMBOL(dma_fence_init);