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![Oded Gabbay](/assets/img/avatar_default.png)
In dma_fence_release() there is a WARN_ON which could be triggered by several cases of wrong dma-fence usage. This patch adds a comment to explain two use-cases to help driver developers that use dma-fence and trigger that WARN_ON to better understand the reasons for it. v2: change to a more generic, one-liner comment Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
577 lines
16 KiB
C
577 lines
16 KiB
C
/*
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* Fence mechanism for dma-buf and to allow for asynchronous dma access
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*
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* Copyright (C) 2012 Canonical Ltd
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* Copyright (C) 2012 Texas Instruments
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*
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* Authors:
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* Rob Clark <robdclark@gmail.com>
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* Maarten Lankhorst <maarten.lankhorst@canonical.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/slab.h>
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#include <linux/export.h>
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#include <linux/atomic.h>
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#include <linux/dma-fence.h>
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#include <linux/sched/signal.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/dma_fence.h>
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EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
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EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
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/*
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* fence context counter: each execution context should have its own
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* fence context, this allows checking if fences belong to the same
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* context or not. One device can have multiple separate contexts,
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* and they're used if some engine can run independently of another.
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*/
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static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(0);
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/**
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* dma_fence_context_alloc - allocate an array of fence contexts
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* @num: [in] amount of contexts to allocate
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*
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* This function will return the first index of the number of fences allocated.
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* The fence context is used for setting fence->context to a unique number.
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*/
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u64 dma_fence_context_alloc(unsigned num)
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{
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WARN_ON(!num);
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return atomic64_add_return(num, &dma_fence_context_counter) - num;
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}
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EXPORT_SYMBOL(dma_fence_context_alloc);
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/**
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* dma_fence_signal_locked - signal completion of a fence
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* @fence: the fence to signal
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*
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* Signal completion for software callbacks on a fence, this will unblock
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* dma_fence_wait() calls and run all the callbacks added with
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* dma_fence_add_callback(). Can be called multiple times, but since a fence
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* can only go from unsignaled to signaled state, it will only be effective
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* the first time.
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*
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* Unlike dma_fence_signal, this function must be called with fence->lock held.
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*/
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int dma_fence_signal_locked(struct dma_fence *fence)
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{
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struct dma_fence_cb *cur, *tmp;
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int ret = 0;
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lockdep_assert_held(fence->lock);
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if (WARN_ON(!fence))
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return -EINVAL;
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if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
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ret = -EINVAL;
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/*
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* we might have raced with the unlocked dma_fence_signal,
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* still run through all callbacks
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*/
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} else {
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fence->timestamp = ktime_get();
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set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
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trace_dma_fence_signaled(fence);
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}
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list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
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list_del_init(&cur->node);
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cur->func(fence, cur);
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}
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return ret;
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}
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EXPORT_SYMBOL(dma_fence_signal_locked);
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/**
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* dma_fence_signal - signal completion of a fence
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* @fence: the fence to signal
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*
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* Signal completion for software callbacks on a fence, this will unblock
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* dma_fence_wait() calls and run all the callbacks added with
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* dma_fence_add_callback(). Can be called multiple times, but since a fence
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* can only go from unsignaled to signaled state, it will only be effective
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* the first time.
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*/
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int dma_fence_signal(struct dma_fence *fence)
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{
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unsigned long flags;
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if (!fence)
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return -EINVAL;
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if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
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return -EINVAL;
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fence->timestamp = ktime_get();
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set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
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trace_dma_fence_signaled(fence);
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if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
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struct dma_fence_cb *cur, *tmp;
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spin_lock_irqsave(fence->lock, flags);
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list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
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list_del_init(&cur->node);
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cur->func(fence, cur);
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}
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spin_unlock_irqrestore(fence->lock, flags);
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}
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return 0;
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}
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EXPORT_SYMBOL(dma_fence_signal);
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/**
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* dma_fence_wait_timeout - sleep until the fence gets signaled
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* or until timeout elapses
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* @fence: [in] the fence to wait on
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* @intr: [in] if true, do an interruptible wait
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* @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
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*
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* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
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* remaining timeout in jiffies on success. Other error values may be
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* returned on custom implementations.
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*
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* Performs a synchronous wait on this fence. It is assumed the caller
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* directly or indirectly (buf-mgr between reservation and committing)
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* holds a reference to the fence, otherwise the fence might be
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* freed before return, resulting in undefined behavior.
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*/
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signed long
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dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
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{
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signed long ret;
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if (WARN_ON(timeout < 0))
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return -EINVAL;
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trace_dma_fence_wait_start(fence);
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ret = fence->ops->wait(fence, intr, timeout);
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trace_dma_fence_wait_end(fence);
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return ret;
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}
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EXPORT_SYMBOL(dma_fence_wait_timeout);
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void dma_fence_release(struct kref *kref)
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{
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struct dma_fence *fence =
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container_of(kref, struct dma_fence, refcount);
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trace_dma_fence_destroy(fence);
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/* Failed to signal before release, could be a refcounting issue */
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WARN_ON(!list_empty(&fence->cb_list));
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if (fence->ops->release)
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fence->ops->release(fence);
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else
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dma_fence_free(fence);
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}
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EXPORT_SYMBOL(dma_fence_release);
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void dma_fence_free(struct dma_fence *fence)
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{
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kfree_rcu(fence, rcu);
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}
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EXPORT_SYMBOL(dma_fence_free);
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/**
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* dma_fence_enable_sw_signaling - enable signaling on fence
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* @fence: [in] the fence to enable
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*
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* this will request for sw signaling to be enabled, to make the fence
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* complete as soon as possible
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*/
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void dma_fence_enable_sw_signaling(struct dma_fence *fence)
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{
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unsigned long flags;
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if (!test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
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&fence->flags) &&
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!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
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trace_dma_fence_enable_signal(fence);
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spin_lock_irqsave(fence->lock, flags);
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if (!fence->ops->enable_signaling(fence))
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dma_fence_signal_locked(fence);
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spin_unlock_irqrestore(fence->lock, flags);
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}
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}
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EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
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/**
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* dma_fence_add_callback - add a callback to be called when the fence
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* is signaled
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* @fence: [in] the fence to wait on
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* @cb: [in] the callback to register
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* @func: [in] the function to call
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*
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* cb will be initialized by dma_fence_add_callback, no initialization
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* by the caller is required. Any number of callbacks can be registered
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* to a fence, but a callback can only be registered to one fence at a time.
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*
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* Note that the callback can be called from an atomic context. If
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* fence is already signaled, this function will return -ENOENT (and
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* *not* call the callback)
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*
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* Add a software callback to the fence. Same restrictions apply to
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* refcount as it does to dma_fence_wait, however the caller doesn't need to
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* keep a refcount to fence afterwards: when software access is enabled,
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* the creator of the fence is required to keep the fence alive until
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* after it signals with dma_fence_signal. The callback itself can be called
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* from irq context.
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*
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* Returns 0 in case of success, -ENOENT if the fence is already signaled
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* and -EINVAL in case of error.
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*/
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int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
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dma_fence_func_t func)
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{
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unsigned long flags;
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int ret = 0;
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bool was_set;
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if (WARN_ON(!fence || !func))
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return -EINVAL;
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if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
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INIT_LIST_HEAD(&cb->node);
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return -ENOENT;
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}
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spin_lock_irqsave(fence->lock, flags);
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was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
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&fence->flags);
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if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
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ret = -ENOENT;
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else if (!was_set) {
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trace_dma_fence_enable_signal(fence);
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if (!fence->ops->enable_signaling(fence)) {
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dma_fence_signal_locked(fence);
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ret = -ENOENT;
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}
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}
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if (!ret) {
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cb->func = func;
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list_add_tail(&cb->node, &fence->cb_list);
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} else
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INIT_LIST_HEAD(&cb->node);
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spin_unlock_irqrestore(fence->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(dma_fence_add_callback);
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/**
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* dma_fence_get_status - returns the status upon completion
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* @fence: [in] the dma_fence to query
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*
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* This wraps dma_fence_get_status_locked() to return the error status
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* condition on a signaled fence. See dma_fence_get_status_locked() for more
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* details.
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*
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* Returns 0 if the fence has not yet been signaled, 1 if the fence has
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* been signaled without an error condition, or a negative error code
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* if the fence has been completed in err.
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*/
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int dma_fence_get_status(struct dma_fence *fence)
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{
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unsigned long flags;
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int status;
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spin_lock_irqsave(fence->lock, flags);
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status = dma_fence_get_status_locked(fence);
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spin_unlock_irqrestore(fence->lock, flags);
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return status;
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}
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EXPORT_SYMBOL(dma_fence_get_status);
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/**
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* dma_fence_remove_callback - remove a callback from the signaling list
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* @fence: [in] the fence to wait on
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* @cb: [in] the callback to remove
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*
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* Remove a previously queued callback from the fence. This function returns
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* true if the callback is successfully removed, or false if the fence has
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* already been signaled.
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*
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* *WARNING*:
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* Cancelling a callback should only be done if you really know what you're
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* doing, since deadlocks and race conditions could occur all too easily. For
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* this reason, it should only ever be done on hardware lockup recovery,
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* with a reference held to the fence.
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*/
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bool
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dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb)
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{
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unsigned long flags;
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bool ret;
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spin_lock_irqsave(fence->lock, flags);
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ret = !list_empty(&cb->node);
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if (ret)
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list_del_init(&cb->node);
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spin_unlock_irqrestore(fence->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(dma_fence_remove_callback);
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struct default_wait_cb {
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struct dma_fence_cb base;
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struct task_struct *task;
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};
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static void
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dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
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{
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struct default_wait_cb *wait =
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container_of(cb, struct default_wait_cb, base);
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wake_up_state(wait->task, TASK_NORMAL);
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}
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/**
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* dma_fence_default_wait - default sleep until the fence gets signaled
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* or until timeout elapses
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* @fence: [in] the fence to wait on
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* @intr: [in] if true, do an interruptible wait
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* @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
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*
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* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
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* remaining timeout in jiffies on success. If timeout is zero the value one is
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* returned if the fence is already signaled for consistency with other
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* functions taking a jiffies timeout.
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*/
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signed long
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dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
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{
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struct default_wait_cb cb;
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unsigned long flags;
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signed long ret = timeout ? timeout : 1;
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bool was_set;
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if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
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return ret;
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spin_lock_irqsave(fence->lock, flags);
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if (intr && signal_pending(current)) {
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ret = -ERESTARTSYS;
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goto out;
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}
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was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
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&fence->flags);
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if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
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goto out;
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if (!was_set) {
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trace_dma_fence_enable_signal(fence);
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if (!fence->ops->enable_signaling(fence)) {
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dma_fence_signal_locked(fence);
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goto out;
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}
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}
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if (!timeout) {
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ret = 0;
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goto out;
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}
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cb.base.func = dma_fence_default_wait_cb;
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cb.task = current;
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list_add(&cb.base.node, &fence->cb_list);
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while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
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if (intr)
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__set_current_state(TASK_INTERRUPTIBLE);
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else
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__set_current_state(TASK_UNINTERRUPTIBLE);
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spin_unlock_irqrestore(fence->lock, flags);
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ret = schedule_timeout(ret);
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spin_lock_irqsave(fence->lock, flags);
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if (ret > 0 && intr && signal_pending(current))
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ret = -ERESTARTSYS;
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}
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if (!list_empty(&cb.base.node))
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list_del(&cb.base.node);
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__set_current_state(TASK_RUNNING);
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out:
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spin_unlock_irqrestore(fence->lock, flags);
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return ret;
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}
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EXPORT_SYMBOL(dma_fence_default_wait);
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static bool
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dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
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uint32_t *idx)
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{
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int i;
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for (i = 0; i < count; ++i) {
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struct dma_fence *fence = fences[i];
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if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
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if (idx)
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*idx = i;
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return true;
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}
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}
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return false;
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}
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/**
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* dma_fence_wait_any_timeout - sleep until any fence gets signaled
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* or until timeout elapses
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* @fences: [in] array of fences to wait on
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* @count: [in] number of fences to wait on
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* @intr: [in] if true, do an interruptible wait
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* @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
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* @idx: [out] the first signaled fence index, meaningful only on
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* positive return
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*
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* Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
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* interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
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* on success.
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*
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* Synchronous waits for the first fence in the array to be signaled. The
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* caller needs to hold a reference to all fences in the array, otherwise a
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* fence might be freed before return, resulting in undefined behavior.
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*/
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signed long
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dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
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bool intr, signed long timeout, uint32_t *idx)
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{
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struct default_wait_cb *cb;
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signed long ret = timeout;
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unsigned i;
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if (WARN_ON(!fences || !count || timeout < 0))
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return -EINVAL;
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if (timeout == 0) {
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for (i = 0; i < count; ++i)
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if (dma_fence_is_signaled(fences[i])) {
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if (idx)
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*idx = i;
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return 1;
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}
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return 0;
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}
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cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
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if (cb == NULL) {
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ret = -ENOMEM;
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goto err_free_cb;
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}
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for (i = 0; i < count; ++i) {
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struct dma_fence *fence = fences[i];
|
|
|
|
if (fence->ops->wait != dma_fence_default_wait) {
|
|
ret = -EINVAL;
|
|
goto fence_rm_cb;
|
|
}
|
|
|
|
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: [in] the fence to initialize
|
|
* @ops: [in] the dma_fence_ops for operations on this fence
|
|
* @lock: [in] the irqsafe spinlock to use for locking this fence
|
|
* @context: [in] the execution context this fence is run on
|
|
* @seqno: [in] 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. This can
|
|
* be used for other implementing other types of fence.
|
|
*
|
|
* 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, unsigned seqno)
|
|
{
|
|
BUG_ON(!lock);
|
|
BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
|
|
!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);
|