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/*
* SPDX-License-Identifier: MIT
*
* Copyright © 2014-2016 Intel Corporation
*/
#include "gt/intel_engine.h"
#include "i915_gem_ioctls.h"
#include "i915_gem_object.h"
static __always_inline u32 __busy_read_flag(u16 id)
{
if (id == (u16)I915_ENGINE_CLASS_INVALID)
return 0xffff0000u;
GEM_BUG_ON(id >= 16);
return 0x10000u << id;
}
static __always_inline u32 __busy_write_id(u16 id)
{
/*
* The uABI guarantees an active writer is also amongst the read
* engines. This would be true if we accessed the activity tracking
* under the lock, but as we perform the lookup of the object and
* its activity locklessly we can not guarantee that the last_write
* being active implies that we have set the same engine flag from
* last_read - hence we always set both read and write busy for
* last_write.
*/
if (id == (u16)I915_ENGINE_CLASS_INVALID)
return 0xffffffffu;
return (id + 1) | __busy_read_flag(id);
}
static __always_inline unsigned int
__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id))
{
const struct i915_request *rq;
/*
* We have to check the current hw status of the fence as the uABI
* guarantees forward progress. We could rely on the idle worker
* to eventually flush us, but to minimise latency just ask the
* hardware.
*
* Note we only report on the status of native fences.
*/
if (!dma_fence_is_i915(fence))
return 0;
/* opencode to_request() in order to avoid const warnings */
rq = container_of(fence, const struct i915_request, fence);
if (i915_request_completed(rq))
return 0;
/* Beware type-expansion follies! */
BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class));
return flag(rq->engine->uabi_class);
}
static __always_inline unsigned int
busy_check_reader(const struct dma_fence *fence)
{
return __busy_set_if_active(fence, __busy_read_flag);
}
static __always_inline unsigned int
busy_check_writer(const struct dma_fence *fence)
{
if (!fence)
return 0;
return __busy_set_if_active(fence, __busy_write_id);
}
int
i915_gem_busy_ioctl(struct drm_device *dev, void *data,
struct drm_file *file)
{
struct drm_i915_gem_busy *args = data;
struct drm_i915_gem_object *obj;
struct dma_resv_list *list;
unsigned int seq;
int err;
err = -ENOENT;
rcu_read_lock();
obj = i915_gem_object_lookup_rcu(file, args->handle);
if (!obj)
goto out;
/*
* A discrepancy here is that we do not report the status of
* non-i915 fences, i.e. even though we may report the object as idle,
* a call to set-domain may still stall waiting for foreign rendering.
* This also means that wait-ioctl may report an object as busy,
* where busy-ioctl considers it idle.
*
* We trade the ability to warn of foreign fences to report on which
* i915 engines are active for the object.
*
* Alternatively, we can trade that extra information on read/write
* activity with
* args->busy =
* !dma_resv_test_signaled_rcu(obj->resv, true);
* to report the overall busyness. This is what the wait-ioctl does.
*
*/
retry:
seq = raw_read_seqcount(&obj->base.resv->seq);
/* Translate the exclusive fence to the READ *and* WRITE engine */
args->busy =
busy_check_writer(rcu_dereference(obj->base.resv->fence_excl));
/* Translate shared fences to READ set of engines */
list = rcu_dereference(obj->base.resv->fence);
if (list) {
unsigned int shared_count = list->shared_count, i;
for (i = 0; i < shared_count; ++i) {
struct dma_fence *fence =
rcu_dereference(list->shared[i]);
args->busy |= busy_check_reader(fence);
}
}
if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
goto retry;
err = 0;
out:
rcu_read_unlock();
return err;
}
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