We can completely avoid taking the struct_mutex around the non-blocking waits by switching over to the RCU request management (trading the mutex for a RCU read lock and some complex atomic operations). The improvement is that we gain further contention reduction, and overall the code become simpler due to the reduced mutex dancing.
Signed-off-by: Chris Wilson <[email protected]> --- drivers/gpu/drm/i915/i915_gem.c | 113 +++++++++++++++++----------------------- 1 file changed, 47 insertions(+), 66 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 4c0e3632214f..76e5a241c7be 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -313,25 +313,20 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj, return 0; } -/* A nonblocking variant of the above wait. This is a highly dangerous routine - * as the object state may change during this call. +/* A nonblocking variant of the above wait. Must be called prior to + * acquiring the mutex for the object, as the object state may change + * during this call. A reference must be held by the caller for the object. */ static __must_check int -i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj, - struct intel_rps_client *rps, - bool readonly) +__unsafe_wait_rendering(struct drm_i915_gem_object *obj, + struct intel_rps_client *rps, + bool readonly) { - struct drm_device *dev = obj->base.dev; - struct drm_i915_private *dev_priv = dev->dev_private; - struct drm_i915_gem_request *requests[I915_NUM_ENGINES]; struct i915_gem_active *active; unsigned long active_mask; - int ret, i, n = 0; - - BUG_ON(!mutex_is_locked(&dev->struct_mutex)); - BUG_ON(!dev_priv->mm.interruptible); + int idx; - active_mask = i915_gem_object_is_active(obj); + active_mask = __I915_BO_ACTIVE(obj); if (!active_mask) return 0; @@ -342,25 +337,16 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj, active = &obj->last_write; } - for_each_active(active_mask, i) { - struct drm_i915_gem_request *req; + for_each_active(active_mask, idx) { + int ret; - req = i915_gem_active_get(&active[i], - &obj->base.dev->struct_mutex); - if (req) - requests[n++] = req; + ret = i915_gem_active_wait_unlocked(&active[idx], + true, NULL, rps); + if (ret) + return ret; } - mutex_unlock(&dev->struct_mutex); - ret = 0; - for (i = 0; ret == 0 && i < n; i++) - ret = __i915_wait_request(requests[i], true, NULL, rps); - mutex_lock(&dev->struct_mutex); - - for (i = 0; i < n; i++) - i915_gem_request_put(requests[i]); - - return ret; + return 0; } static struct intel_rps_client *to_rps_client(struct drm_file *file) @@ -1218,10 +1204,7 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data, int ret; /* Only handle setting domains to types used by the CPU. */ - if (write_domain & I915_GEM_GPU_DOMAINS) - return -EINVAL; - - if (read_domains & I915_GEM_GPU_DOMAINS) + if ((write_domain | read_domains) & I915_GEM_GPU_DOMAINS) return -EINVAL; /* Having something in the write domain implies it's in the read @@ -1230,25 +1213,21 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data, if (write_domain != 0 && read_domains != write_domain) return -EINVAL; - ret = i915_mutex_lock_interruptible(dev); - if (ret) - return ret; - obj = i915_gem_object_lookup(file, args->handle); - if (!obj) { - ret = -ENOENT; - goto unlock; - } + if (!obj) + return -ENOENT; /* Try to flush the object off the GPU without holding the lock. * We will repeat the flush holding the lock in the normal manner * to catch cases where we are gazumped. */ - ret = i915_gem_object_wait_rendering__nonblocking(obj, - to_rps_client(file), - !write_domain); + ret = __unsafe_wait_rendering(obj, to_rps_client(file), !write_domain); + if (ret) + goto out_unlocked; + + ret = i915_mutex_lock_interruptible(dev); if (ret) - goto unref; + goto out_unlocked; if (read_domains & I915_GEM_DOMAIN_GTT) ret = i915_gem_object_set_to_gtt_domain(obj, write_domain != 0); @@ -1260,11 +1239,13 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data, write_domain == I915_GEM_DOMAIN_GTT ? ORIGIN_GTT : ORIGIN_CPU); -unref: i915_gem_object_put(obj); -unlock: mutex_unlock(&dev->struct_mutex); return ret; + +out_unlocked: + i915_gem_object_put_unlocked(obj); + return ret; } /** @@ -1397,6 +1378,15 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) int ret = 0; bool write = !!(vmf->flags & FAULT_FLAG_WRITE); + /* Try to flush the object off the GPU first without holding the lock. + * Upon acquiring the lock, we will perform our sanity checks and then + * repeat the flush holding the lock in the normal manner to catch cases + * where we are gazumped. + */ + ret = __unsafe_wait_rendering(obj, NULL, !write); + if (ret) + goto err; + intel_runtime_pm_get(dev_priv); /* We don't use vmf->pgoff since that has the fake offset */ @@ -1405,23 +1395,14 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) ret = i915_mutex_lock_interruptible(dev); if (ret) - goto out; + goto err_rpm; trace_i915_gem_object_fault(obj, page_offset, true, write); - /* Try to flush the object off the GPU first without holding the lock. - * Upon reacquiring the lock, we will perform our sanity checks and then - * repeat the flush holding the lock in the normal manner to catch cases - * where we are gazumped. - */ - ret = i915_gem_object_wait_rendering__nonblocking(obj, NULL, !write); - if (ret) - goto unlock; - /* Access to snoopable pages through the GTT is incoherent. */ if (obj->cache_level != I915_CACHE_NONE && !HAS_LLC(dev)) { ret = -EFAULT; - goto unlock; + goto err_unlock; } /* Use a partial view if the object is bigger than the aperture. */ @@ -1442,15 +1423,15 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) /* Now pin it into the GTT if needed */ ret = i915_gem_object_ggtt_pin(obj, &view, 0, 0, PIN_MAPPABLE); if (ret) - goto unlock; + goto err_unlock; ret = i915_gem_object_set_to_gtt_domain(obj, write); if (ret) - goto unpin; + goto err_unpin; ret = i915_gem_object_get_fence(obj); if (ret) - goto unpin; + goto err_unpin; /* Finally, remap it using the new GTT offset */ pfn = ggtt->mappable_base + @@ -1495,11 +1476,13 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) (unsigned long)vmf->virtual_address, pfn + page_offset); } -unpin: +err_unpin: i915_gem_object_ggtt_unpin_view(obj, &view); -unlock: +err_unlock: mutex_unlock(&dev->struct_mutex); -out: +err_rpm: + intel_runtime_pm_put(dev_priv); +err: switch (ret) { case -EIO: /* @@ -1540,8 +1523,6 @@ out: ret = VM_FAULT_SIGBUS; break; } - - intel_runtime_pm_put(dev_priv); return ret; } -- 2.8.1 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
