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8f94eda399
This should be possible now since we don't have the distinction between exclusive and shared fences any more. The only possible pitfall is that a dma_fence would be reused during the RCU grace period, but even that could be handled with a single extra check. Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-15-christian.koenig@amd.com
475 lines
16 KiB
C
475 lines
16 KiB
C
/*
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* Header file for reservations for dma-buf and ttm
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*
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* Copyright(C) 2011 Linaro Limited. All rights reserved.
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* Copyright (C) 2012-2013 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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* Thomas Hellstrom <thellstrom-at-vmware-dot-com>
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*
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* Based on bo.c which bears the following copyright notice,
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* but is dual licensed:
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*
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* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sub license, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial portions
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* of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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* USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef _LINUX_RESERVATION_H
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#define _LINUX_RESERVATION_H
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#include <linux/ww_mutex.h>
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#include <linux/dma-fence.h>
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#include <linux/slab.h>
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#include <linux/seqlock.h>
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#include <linux/rcupdate.h>
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extern struct ww_class reservation_ww_class;
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struct dma_resv_list;
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/**
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* enum dma_resv_usage - how the fences from a dma_resv obj are used
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*
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* This enum describes the different use cases for a dma_resv object and
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* controls which fences are returned when queried.
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*
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* An important fact is that there is the order KERNEL<WRITE<READ<BOOKKEEP and
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* when the dma_resv object is asked for fences for one use case the fences
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* for the lower use case are returned as well.
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*
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* For example when asking for WRITE fences then the KERNEL fences are returned
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* as well. Similar when asked for READ fences then both WRITE and KERNEL
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* fences are returned as well.
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*/
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enum dma_resv_usage {
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/**
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* @DMA_RESV_USAGE_KERNEL: For in kernel memory management only.
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*
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* This should only be used for things like copying or clearing memory
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* with a DMA hardware engine for the purpose of kernel memory
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* management.
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*
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* Drivers *always* must wait for those fences before accessing the
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* resource protected by the dma_resv object. The only exception for
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* that is when the resource is known to be locked down in place by
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* pinning it previously.
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*/
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DMA_RESV_USAGE_KERNEL,
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/**
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* @DMA_RESV_USAGE_WRITE: Implicit write synchronization.
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*
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* This should only be used for userspace command submissions which add
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* an implicit write dependency.
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*/
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DMA_RESV_USAGE_WRITE,
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/**
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* @DMA_RESV_USAGE_READ: Implicit read synchronization.
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*
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* This should only be used for userspace command submissions which add
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* an implicit read dependency.
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*/
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DMA_RESV_USAGE_READ,
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/**
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* @DMA_RESV_USAGE_BOOKKEEP: No implicit sync.
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*
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* This should be used by submissions which don't want to participate in
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* implicit synchronization.
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*
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* The most common case are preemption fences as well as page table
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* updates and their TLB flushes.
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*/
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DMA_RESV_USAGE_BOOKKEEP
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};
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/**
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* dma_resv_usage_rw - helper for implicit sync
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* @write: true if we create a new implicit sync write
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*
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* This returns the implicit synchronization usage for write or read accesses,
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* see enum dma_resv_usage and &dma_buf.resv.
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*/
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static inline enum dma_resv_usage dma_resv_usage_rw(bool write)
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{
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/* This looks confusing at first sight, but is indeed correct.
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*
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* The rational is that new write operations needs to wait for the
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* existing read and write operations to finish.
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* But a new read operation only needs to wait for the existing write
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* operations to finish.
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*/
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return write ? DMA_RESV_USAGE_READ : DMA_RESV_USAGE_WRITE;
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}
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/**
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* struct dma_resv - a reservation object manages fences for a buffer
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*
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* This is a container for dma_fence objects which needs to handle multiple use
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* cases.
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*
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* One use is to synchronize cross-driver access to a struct dma_buf, either for
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* dynamic buffer management or just to handle implicit synchronization between
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* different users of the buffer in userspace. See &dma_buf.resv for a more
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* in-depth discussion.
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*
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* The other major use is to manage access and locking within a driver in a
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* buffer based memory manager. struct ttm_buffer_object is the canonical
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* example here, since this is where reservation objects originated from. But
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* use in drivers is spreading and some drivers also manage struct
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* drm_gem_object with the same scheme.
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*/
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struct dma_resv {
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/**
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* @lock:
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*
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* Update side lock. Don't use directly, instead use the wrapper
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* functions like dma_resv_lock() and dma_resv_unlock().
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*
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* Drivers which use the reservation object to manage memory dynamically
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* also use this lock to protect buffer object state like placement,
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* allocation policies or throughout command submission.
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*/
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struct ww_mutex lock;
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/**
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* @fences:
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*
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* Array of fences which where added to the dma_resv object
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*
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* A new fence is added by calling dma_resv_add_fence(). Since this
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* often needs to be done past the point of no return in command
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* submission it cannot fail, and therefore sufficient slots need to be
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* reserved by calling dma_resv_reserve_fences().
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*/
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struct dma_resv_list __rcu *fences;
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};
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/**
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* struct dma_resv_iter - current position into the dma_resv fences
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*
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* Don't touch this directly in the driver, use the accessor function instead.
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*
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* IMPORTANT
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*
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* When using the lockless iterators like dma_resv_iter_next_unlocked() or
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* dma_resv_for_each_fence_unlocked() beware that the iterator can be restarted.
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* Code which accumulates statistics or similar needs to check for this with
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* dma_resv_iter_is_restarted().
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*/
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struct dma_resv_iter {
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/** @obj: The dma_resv object we iterate over */
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struct dma_resv *obj;
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/** @usage: Return fences with this usage or lower. */
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enum dma_resv_usage usage;
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/** @fence: the currently handled fence */
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struct dma_fence *fence;
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/** @fence_usage: the usage of the current fence */
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enum dma_resv_usage fence_usage;
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/** @index: index into the shared fences */
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unsigned int index;
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/** @fences: the shared fences; private, *MUST* not dereference */
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struct dma_resv_list *fences;
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/** @num_fences: number of fences */
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unsigned int num_fences;
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/** @is_restarted: true if this is the first returned fence */
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bool is_restarted;
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};
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struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor);
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struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor);
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struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
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struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
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/**
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* dma_resv_iter_begin - initialize a dma_resv_iter object
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* @cursor: The dma_resv_iter object to initialize
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* @obj: The dma_resv object which we want to iterate over
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* @usage: controls which fences to include, see enum dma_resv_usage.
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*/
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static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
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struct dma_resv *obj,
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enum dma_resv_usage usage)
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{
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cursor->obj = obj;
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cursor->usage = usage;
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cursor->fence = NULL;
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}
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/**
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* dma_resv_iter_end - cleanup a dma_resv_iter object
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* @cursor: the dma_resv_iter object which should be cleaned up
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*
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* Make sure that the reference to the fence in the cursor is properly
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* dropped.
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*/
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static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
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{
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dma_fence_put(cursor->fence);
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}
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/**
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* dma_resv_iter_usage - Return the usage of the current fence
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* @cursor: the cursor of the current position
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*
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* Returns the usage of the currently processed fence.
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*/
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static inline enum dma_resv_usage
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dma_resv_iter_usage(struct dma_resv_iter *cursor)
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{
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return cursor->fence_usage;
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}
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/**
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* dma_resv_iter_is_restarted - test if this is the first fence after a restart
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* @cursor: the cursor with the current position
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*
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* Return true if this is the first fence in an iteration after a restart.
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*/
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static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
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{
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return cursor->is_restarted;
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}
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/**
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* dma_resv_for_each_fence_unlocked - unlocked fence iterator
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* @cursor: a struct dma_resv_iter pointer
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* @fence: the current fence
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*
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* Iterate over the fences in a struct dma_resv object without holding the
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* &dma_resv.lock and using RCU instead. The cursor needs to be initialized
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* with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside
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* the iterator a reference to the dma_fence is held and the RCU lock dropped.
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*
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* Beware that the iterator can be restarted when the struct dma_resv for
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* @cursor is modified. Code which accumulates statistics or similar needs to
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* check for this with dma_resv_iter_is_restarted(). For this reason prefer the
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* lock iterator dma_resv_for_each_fence() whenever possible.
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*/
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#define dma_resv_for_each_fence_unlocked(cursor, fence) \
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for (fence = dma_resv_iter_first_unlocked(cursor); \
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fence; fence = dma_resv_iter_next_unlocked(cursor))
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/**
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* dma_resv_for_each_fence - fence iterator
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* @cursor: a struct dma_resv_iter pointer
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* @obj: a dma_resv object pointer
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* @usage: controls which fences to return
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* @fence: the current fence
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*
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* Iterate over the fences in a struct dma_resv object while holding the
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* &dma_resv.lock. @all_fences controls if the shared fences are returned as
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* well. The cursor initialisation is part of the iterator and the fence stays
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* valid as long as the lock is held and so no extra reference to the fence is
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* taken.
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*/
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#define dma_resv_for_each_fence(cursor, obj, usage, fence) \
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for (dma_resv_iter_begin(cursor, obj, usage), \
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fence = dma_resv_iter_first(cursor); fence; \
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fence = dma_resv_iter_next(cursor))
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#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
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#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
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#ifdef CONFIG_DEBUG_MUTEXES
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void dma_resv_reset_max_fences(struct dma_resv *obj);
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#else
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static inline void dma_resv_reset_max_fences(struct dma_resv *obj) {}
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#endif
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/**
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* dma_resv_lock - lock the reservation object
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* @obj: the reservation object
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* @ctx: the locking context
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*
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* Locks the reservation object for exclusive access and modification. Note,
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* that the lock is only against other writers, readers will run concurrently
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* with a writer under RCU. The seqlock is used to notify readers if they
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* overlap with a writer.
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*
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* As the reservation object may be locked by multiple parties in an
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* undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
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* is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
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* object may be locked by itself by passing NULL as @ctx.
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*
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* When a die situation is indicated by returning -EDEADLK all locks held by
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* @ctx must be unlocked and then dma_resv_lock_slow() called on @obj.
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*
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* Unlocked by calling dma_resv_unlock().
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*
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* See also dma_resv_lock_interruptible() for the interruptible variant.
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*/
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static inline int dma_resv_lock(struct dma_resv *obj,
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struct ww_acquire_ctx *ctx)
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{
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return ww_mutex_lock(&obj->lock, ctx);
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}
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/**
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* dma_resv_lock_interruptible - lock the reservation object
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* @obj: the reservation object
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* @ctx: the locking context
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*
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* Locks the reservation object interruptible for exclusive access and
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* modification. Note, that the lock is only against other writers, readers
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* will run concurrently with a writer under RCU. The seqlock is used to
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* notify readers if they overlap with a writer.
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*
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* As the reservation object may be locked by multiple parties in an
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* undefined order, a #ww_acquire_ctx is passed to unwind if a cycle
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* is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
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* object may be locked by itself by passing NULL as @ctx.
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*
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* When a die situation is indicated by returning -EDEADLK all locks held by
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* @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on
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* @obj.
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*
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* Unlocked by calling dma_resv_unlock().
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*/
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static inline int dma_resv_lock_interruptible(struct dma_resv *obj,
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struct ww_acquire_ctx *ctx)
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{
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return ww_mutex_lock_interruptible(&obj->lock, ctx);
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}
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/**
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* dma_resv_lock_slow - slowpath lock the reservation object
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* @obj: the reservation object
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* @ctx: the locking context
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*
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* Acquires the reservation object after a die case. This function
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* will sleep until the lock becomes available. See dma_resv_lock() as
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* well.
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*
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* See also dma_resv_lock_slow_interruptible() for the interruptible variant.
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*/
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static inline void dma_resv_lock_slow(struct dma_resv *obj,
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struct ww_acquire_ctx *ctx)
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{
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ww_mutex_lock_slow(&obj->lock, ctx);
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}
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/**
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* dma_resv_lock_slow_interruptible - slowpath lock the reservation
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* object, interruptible
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* @obj: the reservation object
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* @ctx: the locking context
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*
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* Acquires the reservation object interruptible after a die case. This function
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* will sleep until the lock becomes available. See
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* dma_resv_lock_interruptible() as well.
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*/
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static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
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struct ww_acquire_ctx *ctx)
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{
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return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
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}
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/**
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* dma_resv_trylock - trylock the reservation object
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* @obj: the reservation object
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*
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* Tries to lock the reservation object for exclusive access and modification.
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* Note, that the lock is only against other writers, readers will run
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* concurrently with a writer under RCU. The seqlock is used to notify readers
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* if they overlap with a writer.
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*
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* Also note that since no context is provided, no deadlock protection is
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* possible, which is also not needed for a trylock.
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*
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* Returns true if the lock was acquired, false otherwise.
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*/
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static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
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{
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return ww_mutex_trylock(&obj->lock, NULL);
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}
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/**
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* dma_resv_is_locked - is the reservation object locked
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* @obj: the reservation object
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*
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* Returns true if the mutex is locked, false if unlocked.
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*/
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static inline bool dma_resv_is_locked(struct dma_resv *obj)
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{
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return ww_mutex_is_locked(&obj->lock);
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}
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/**
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* dma_resv_locking_ctx - returns the context used to lock the object
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* @obj: the reservation object
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*
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* Returns the context used to lock a reservation object or NULL if no context
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* was used or the object is not locked at all.
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*
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* WARNING: This interface is pretty horrible, but TTM needs it because it
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* doesn't pass the struct ww_acquire_ctx around in some very long callchains.
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* Everyone else just uses it to check whether they're holding a reservation or
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* not.
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*/
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static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj)
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{
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return READ_ONCE(obj->lock.ctx);
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}
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/**
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* dma_resv_unlock - unlock the reservation object
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* @obj: the reservation object
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*
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* Unlocks the reservation object following exclusive access.
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*/
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static inline void dma_resv_unlock(struct dma_resv *obj)
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{
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dma_resv_reset_max_fences(obj);
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ww_mutex_unlock(&obj->lock);
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}
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void dma_resv_init(struct dma_resv *obj);
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void dma_resv_fini(struct dma_resv *obj);
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int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences);
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void dma_resv_add_fence(struct dma_resv *obj, struct dma_fence *fence,
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enum dma_resv_usage usage);
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void dma_resv_replace_fences(struct dma_resv *obj, uint64_t context,
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struct dma_fence *fence,
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enum dma_resv_usage usage);
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int dma_resv_get_fences(struct dma_resv *obj, enum dma_resv_usage usage,
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unsigned int *num_fences, struct dma_fence ***fences);
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int dma_resv_get_singleton(struct dma_resv *obj, enum dma_resv_usage usage,
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struct dma_fence **fence);
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int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src);
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long dma_resv_wait_timeout(struct dma_resv *obj, enum dma_resv_usage usage,
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bool intr, unsigned long timeout);
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bool dma_resv_test_signaled(struct dma_resv *obj, enum dma_resv_usage usage);
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void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq);
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#endif /* _LINUX_RESERVATION_H */
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