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b1e3177bd1
Forgo the struct_mutex serialisation for i915_active, and interpose its own mutex handling for active/retire. This is a multi-layered sleight-of-hand. First, we had to ensure that no active/retire callbacks accidentally inverted the mutex ordering rules, nor assumed that they were themselves serialised by struct_mutex. More challenging though, is the rule over updating elements of the active rbtree. Instead of the whole i915_active now being serialised by struct_mutex, allocations/rotations of the tree are serialised by the i915_active.mutex and individual nodes are serialised by the caller using the i915_timeline.mutex (we need to use nested spinlocks to interact with the dma_fence callback lists). The pain point here is that instead of a single mutex around execbuf, we now have to take a mutex for active tracker (one for each vma, context, etc) and a couple of spinlocks for each fence update. The improvement in fine grained locking allowing for multiple concurrent clients (eventually!) should be worth it in typical loads. v2: Add some comments that barely elucidate anything :( Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-6-chris@chris-wilson.co.uk
68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/*
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* SPDX-License-Identifier: MIT
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*
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* Copyright © 2019 Intel Corporation
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*/
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#ifndef _I915_ACTIVE_TYPES_H_
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#define _I915_ACTIVE_TYPES_H_
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#include <linux/atomic.h>
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#include <linux/dma-fence.h>
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#include <linux/llist.h>
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#include <linux/mutex.h>
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#include <linux/rbtree.h>
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#include <linux/rcupdate.h>
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#include <linux/workqueue.h>
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#include "i915_utils.h"
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struct i915_active_fence {
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struct dma_fence __rcu *fence;
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struct dma_fence_cb cb;
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#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
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/*
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* Incorporeal!
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*
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* Updates to the i915_active_request must be serialised under a lock
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* to ensure that the timeline is ordered. Normally, this is the
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* timeline->mutex, but another mutex may be used so long as it is
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* done so consistently.
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*
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* For lockdep tracking of the above, we store the lock we intend
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* to always use for updates of this i915_active_request during
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* construction and assert that is held on every update.
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*/
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struct mutex *lock;
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#endif
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};
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struct active_node;
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#define I915_ACTIVE_MAY_SLEEP BIT(0)
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#define __i915_active_call __aligned(4)
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#define i915_active_may_sleep(fn) ptr_pack_bits(&(fn), I915_ACTIVE_MAY_SLEEP, 2)
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struct i915_active {
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atomic_t count;
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struct mutex mutex;
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struct active_node *cache;
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struct rb_root tree;
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/* Preallocated "exclusive" node */
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struct i915_active_fence excl;
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unsigned long flags;
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#define I915_ACTIVE_RETIRE_SLEEPS BIT(0)
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int (*active)(struct i915_active *ref);
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void (*retire)(struct i915_active *ref);
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struct work_struct work;
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struct llist_head preallocated_barriers;
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};
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#endif /* _I915_ACTIVE_TYPES_H_ */
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