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Ages ago Rob Clark noted, "Currently with fence-array, we have a potential deadlock situation. If we fence_add_callback() on an array-fence, the array-fence's lock is acquired first, and in it's ->enable_signaling() callback, it will install cbs on it's array-member fences, so the array-member's lock is acquired second. But in the signal path, the array-member's lock is acquired first, and the array-fence's lock acquired second." Rob proposed either extensive changes to dma-fence to unnest the fence-array signaling, or to defer the signaling onto a workqueue. This is a more refined version of the later, that should keep the latency of the fence signaling to a minimum by using an irq-work, which is executed asap. Reported-by: Rob Clark <robdclark@gmail.com> Suggested-by: Rob Clark <robdclark@gmail.com> References: 1476635975-21981-1-git-send-email-robdclark@gmail.com Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Rob Clark <robdclark@gmail.com> Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Christian König <christian.koenig@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20171114162719.30958-1-chris@chris-wilson.co.uk
92 lines
2.5 KiB
C
92 lines
2.5 KiB
C
/*
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* fence-array: aggregates fence to be waited together
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*
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* Copyright (C) 2016 Collabora Ltd
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* Copyright (C) 2016 Advanced Micro Devices, Inc.
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* Authors:
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* Gustavo Padovan <gustavo@padovan.org>
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* Christian König <christian.koenig@amd.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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#ifndef __LINUX_DMA_FENCE_ARRAY_H
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#define __LINUX_DMA_FENCE_ARRAY_H
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#include <linux/dma-fence.h>
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#include <linux/irq_work.h>
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/**
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* struct dma_fence_array_cb - callback helper for fence array
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* @cb: fence callback structure for signaling
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* @array: reference to the parent fence array object
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*/
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struct dma_fence_array_cb {
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struct dma_fence_cb cb;
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struct dma_fence_array *array;
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};
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/**
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* struct dma_fence_array - fence to represent an array of fences
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* @base: fence base class
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* @lock: spinlock for fence handling
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* @num_fences: number of fences in the array
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* @num_pending: fences in the array still pending
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* @fences: array of the fences
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*/
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struct dma_fence_array {
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struct dma_fence base;
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spinlock_t lock;
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unsigned num_fences;
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atomic_t num_pending;
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struct dma_fence **fences;
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struct irq_work work;
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};
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extern const struct dma_fence_ops dma_fence_array_ops;
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/**
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* dma_fence_is_array - check if a fence is from the array subsclass
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* @fence: fence to test
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*
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* Return true if it is a dma_fence_array and false otherwise.
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*/
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static inline bool dma_fence_is_array(struct dma_fence *fence)
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{
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return fence->ops == &dma_fence_array_ops;
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}
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/**
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* to_dma_fence_array - cast a fence to a dma_fence_array
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* @fence: fence to cast to a dma_fence_array
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*
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* Returns NULL if the fence is not a dma_fence_array,
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* or the dma_fence_array otherwise.
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*/
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static inline struct dma_fence_array *
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to_dma_fence_array(struct dma_fence *fence)
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{
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if (fence->ops != &dma_fence_array_ops)
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return NULL;
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return container_of(fence, struct dma_fence_array, base);
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}
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struct dma_fence_array *dma_fence_array_create(int num_fences,
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struct dma_fence **fences,
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u64 context, unsigned seqno,
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bool signal_on_any);
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bool dma_fence_match_context(struct dma_fence *fence, u64 context);
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#endif /* __LINUX_DMA_FENCE_ARRAY_H */
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