mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-24 01:41:39 +00:00
![Chris Wilson](/assets/img/avatar_default.png)
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
217 lines
7.6 KiB
C
217 lines
7.6 KiB
C
/*
|
|
* SPDX-License-Identifier: MIT
|
|
*
|
|
* Copyright © 2019 Intel Corporation
|
|
*/
|
|
|
|
#ifndef _I915_ACTIVE_H_
|
|
#define _I915_ACTIVE_H_
|
|
|
|
#include <linux/lockdep.h>
|
|
|
|
#include "i915_active_types.h"
|
|
#include "i915_request.h"
|
|
|
|
struct i915_request;
|
|
struct intel_engine_cs;
|
|
struct intel_timeline;
|
|
|
|
/*
|
|
* We treat requests as fences. This is not be to confused with our
|
|
* "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
|
|
* We use the fences to synchronize access from the CPU with activity on the
|
|
* GPU, for example, we should not rewrite an object's PTE whilst the GPU
|
|
* is reading them. We also track fences at a higher level to provide
|
|
* implicit synchronisation around GEM objects, e.g. set-domain will wait
|
|
* for outstanding GPU rendering before marking the object ready for CPU
|
|
* access, or a pageflip will wait until the GPU is complete before showing
|
|
* the frame on the scanout.
|
|
*
|
|
* In order to use a fence, the object must track the fence it needs to
|
|
* serialise with. For example, GEM objects want to track both read and
|
|
* write access so that we can perform concurrent read operations between
|
|
* the CPU and GPU engines, as well as waiting for all rendering to
|
|
* complete, or waiting for the last GPU user of a "fence register". The
|
|
* object then embeds a #i915_active_fence to track the most recent (in
|
|
* retirement order) request relevant for the desired mode of access.
|
|
* The #i915_active_fence is updated with i915_active_fence_set() to
|
|
* track the most recent fence request, typically this is done as part of
|
|
* i915_vma_move_to_active().
|
|
*
|
|
* When the #i915_active_fence completes (is retired), it will
|
|
* signal its completion to the owner through a callback as well as mark
|
|
* itself as idle (i915_active_fence.request == NULL). The owner
|
|
* can then perform any action, such as delayed freeing of an active
|
|
* resource including itself.
|
|
*/
|
|
|
|
void i915_active_noop(struct dma_fence *fence, struct dma_fence_cb *cb);
|
|
|
|
/**
|
|
* __i915_active_fence_init - prepares the activity tracker for use
|
|
* @active - the active tracker
|
|
* @fence - initial fence to track, can be NULL
|
|
* @func - a callback when then the tracker is retired (becomes idle),
|
|
* can be NULL
|
|
*
|
|
* i915_active_fence_init() prepares the embedded @active struct for use as
|
|
* an activity tracker, that is for tracking the last known active fence
|
|
* associated with it. When the last fence becomes idle, when it is retired
|
|
* after completion, the optional callback @func is invoked.
|
|
*/
|
|
static inline void
|
|
__i915_active_fence_init(struct i915_active_fence *active,
|
|
struct mutex *lock,
|
|
void *fence,
|
|
dma_fence_func_t fn)
|
|
{
|
|
RCU_INIT_POINTER(active->fence, fence);
|
|
active->cb.func = fn ?: i915_active_noop;
|
|
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
|
|
active->lock = lock;
|
|
#endif
|
|
}
|
|
|
|
#define INIT_ACTIVE_FENCE(A, LOCK) \
|
|
__i915_active_fence_init((A), (LOCK), NULL, NULL)
|
|
|
|
struct dma_fence *
|
|
__i915_active_fence_set(struct i915_active_fence *active,
|
|
struct dma_fence *fence);
|
|
|
|
/**
|
|
* i915_active_fence_set - updates the tracker to watch the current fence
|
|
* @active - the active tracker
|
|
* @rq - the request to watch
|
|
*
|
|
* i915_active_fence_set() watches the given @rq for completion. While
|
|
* that @rq is busy, the @active reports busy. When that @rq is signaled
|
|
* (or else retired) the @active tracker is updated to report idle.
|
|
*/
|
|
int __must_check
|
|
i915_active_fence_set(struct i915_active_fence *active,
|
|
struct i915_request *rq);
|
|
/**
|
|
* i915_active_fence_get - return a reference to the active fence
|
|
* @active - the active tracker
|
|
*
|
|
* i915_active_fence_get() returns a reference to the active fence,
|
|
* or NULL if the active tracker is idle. The reference is obtained under RCU,
|
|
* so no locking is required by the caller.
|
|
*
|
|
* The reference should be freed with dma_fence_put().
|
|
*/
|
|
static inline struct dma_fence *
|
|
i915_active_fence_get(struct i915_active_fence *active)
|
|
{
|
|
struct dma_fence *fence;
|
|
|
|
rcu_read_lock();
|
|
fence = dma_fence_get_rcu_safe(&active->fence);
|
|
rcu_read_unlock();
|
|
|
|
return fence;
|
|
}
|
|
|
|
/**
|
|
* i915_active_fence_isset - report whether the active tracker is assigned
|
|
* @active - the active tracker
|
|
*
|
|
* i915_active_fence_isset() returns true if the active tracker is currently
|
|
* assigned to a fence. Due to the lazy retiring, that fence may be idle
|
|
* and this may report stale information.
|
|
*/
|
|
static inline bool
|
|
i915_active_fence_isset(const struct i915_active_fence *active)
|
|
{
|
|
return rcu_access_pointer(active->fence);
|
|
}
|
|
|
|
static inline void
|
|
i915_active_fence_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
|
|
{
|
|
struct i915_active_fence *active =
|
|
container_of(cb, typeof(*active), cb);
|
|
|
|
RCU_INIT_POINTER(active->fence, NULL);
|
|
}
|
|
|
|
/*
|
|
* GPU activity tracking
|
|
*
|
|
* Each set of commands submitted to the GPU compromises a single request that
|
|
* signals a fence upon completion. struct i915_request combines the
|
|
* command submission, scheduling and fence signaling roles. If we want to see
|
|
* if a particular task is complete, we need to grab the fence (struct
|
|
* i915_request) for that task and check or wait for it to be signaled. More
|
|
* often though we want to track the status of a bunch of tasks, for example
|
|
* to wait for the GPU to finish accessing some memory across a variety of
|
|
* different command pipelines from different clients. We could choose to
|
|
* track every single request associated with the task, but knowing that
|
|
* each request belongs to an ordered timeline (later requests within a
|
|
* timeline must wait for earlier requests), we need only track the
|
|
* latest request in each timeline to determine the overall status of the
|
|
* task.
|
|
*
|
|
* struct i915_active provides this tracking across timelines. It builds a
|
|
* composite shared-fence, and is updated as new work is submitted to the task,
|
|
* forming a snapshot of the current status. It should be embedded into the
|
|
* different resources that need to track their associated GPU activity to
|
|
* provide a callback when that GPU activity has ceased, or otherwise to
|
|
* provide a serialisation point either for request submission or for CPU
|
|
* synchronisation.
|
|
*/
|
|
|
|
void __i915_active_init(struct i915_active *ref,
|
|
int (*active)(struct i915_active *ref),
|
|
void (*retire)(struct i915_active *ref),
|
|
struct lock_class_key *key);
|
|
#define i915_active_init(ref, active, retire) do { \
|
|
static struct lock_class_key __key; \
|
|
\
|
|
__i915_active_init(ref, active, retire, &__key); \
|
|
} while (0)
|
|
|
|
int i915_active_ref(struct i915_active *ref,
|
|
struct intel_timeline *tl,
|
|
struct dma_fence *fence);
|
|
|
|
static inline int
|
|
i915_active_add_request(struct i915_active *ref, struct i915_request *rq)
|
|
{
|
|
return i915_active_ref(ref, i915_request_timeline(rq), &rq->fence);
|
|
}
|
|
|
|
void i915_active_set_exclusive(struct i915_active *ref, struct dma_fence *f);
|
|
|
|
static inline bool i915_active_has_exclusive(struct i915_active *ref)
|
|
{
|
|
return rcu_access_pointer(ref->excl.fence);
|
|
}
|
|
|
|
int i915_active_wait(struct i915_active *ref);
|
|
|
|
int i915_request_await_active(struct i915_request *rq, struct i915_active *ref);
|
|
|
|
int i915_active_acquire(struct i915_active *ref);
|
|
bool i915_active_acquire_if_busy(struct i915_active *ref);
|
|
void i915_active_release(struct i915_active *ref);
|
|
|
|
static inline bool
|
|
i915_active_is_idle(const struct i915_active *ref)
|
|
{
|
|
return !atomic_read(&ref->count);
|
|
}
|
|
|
|
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM)
|
|
void i915_active_fini(struct i915_active *ref);
|
|
#else
|
|
static inline void i915_active_fini(struct i915_active *ref) { }
|
|
#endif
|
|
|
|
int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
|
|
struct intel_engine_cs *engine);
|
|
void i915_active_acquire_barrier(struct i915_active *ref);
|
|
void i915_request_add_active_barriers(struct i915_request *rq);
|
|
|
|
#endif /* _I915_ACTIVE_H_ */
|