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![Christian König](/assets/img/avatar_default.png)
Add an usage for kernel submissions. Waiting for those are mandatory for dynamic DMA-bufs. As a precaution this patch also changes all occurrences where fences are added as part of memory management in TTM, VMWGFX and i915 to use the new value because it now becomes possible for drivers to ignore fences with the WRITE usage. v2: use "must" in documentation, fix whitespaces v3: separate out some driver changes and better document why some changes should still be part of this patch. Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-5-christian.koenig@amd.com
476 lines
16 KiB
C
476 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 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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/**
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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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* @seq:
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*
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* Sequence count for managing RCU read-side synchronization, allows
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* read-only access to @fences while ensuring we take a consistent
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* snapshot.
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*/
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seqcount_ww_mutex_t seq;
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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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/** @seq: sequence number to check for modifications */
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unsigned int seq;
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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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