From 2467658e2de3ca1dee6688b6b0b6f48263dfd532 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 5 Aug 2016 10:14:06 +0100 Subject: [PATCH] drm/i915: Introduce i915_gem_active_wait_unlocked() It is useful to be able to wait on pending rendering without grabbing the struct_mutex. We can do this by using the i915_gem_active_get_rcu() primitive to acquire a reference to the pending request without requiring struct_mutex, just the RCU read lock, and then call i915_wait_request(). v2: Rebase onto new i915_gem_active_get_unlocked() semantics that take the RCU read lock on behalf of the caller. Signed-off-by: Chris Wilson Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-1-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem_request.h | 40 +++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h index 6002adc43523..15495d1e48e8 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.h +++ b/drivers/gpu/drm/i915/i915_gem_request.h @@ -568,6 +568,46 @@ i915_gem_active_wait(const struct i915_gem_active *active, struct mutex *mutex) return i915_wait_request(request, true, NULL, NULL); } +/** + * i915_gem_active_wait_unlocked - waits until the request is completed + * @active - the active request on which to wait + * @interruptible - whether the wait can be woken by a userspace signal + * @timeout - how long to wait at most + * @rps - userspace client to charge for a waitboost + * + * i915_gem_active_wait_unlocked() waits until the request is completed before + * returning, without requiring any locks to be held. Note that it does not + * retire any requests before returning. + * + * This function relies on RCU in order to acquire the reference to the active + * request without holding any locks. See __i915_gem_active_get_rcu() for the + * glory details on how that is managed. Once the reference is acquired, we + * can then wait upon the request, and afterwards release our reference, + * free of any locking. + * + * This function wraps i915_wait_request(), see it for the full details on + * the arguments. + * + * Returns 0 if successful, or a negative error code. + */ +static inline int +i915_gem_active_wait_unlocked(const struct i915_gem_active *active, + bool interruptible, + s64 *timeout, + struct intel_rps_client *rps) +{ + struct drm_i915_gem_request *request; + int ret = 0; + + request = i915_gem_active_get_unlocked(active); + if (request) { + ret = i915_wait_request(request, interruptible, timeout, rps); + i915_gem_request_put(request); + } + + return ret; +} + /** * i915_gem_active_retire - waits until the request is retired * @active - the active request on which to wait -- 2.30.2