diff options
Diffstat (limited to 'drivers/gpu/drm/i915/i915_gem_request.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_request.h | 61 |
1 files changed, 31 insertions, 30 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h index 3496e28..6c72bd8 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.h +++ b/drivers/gpu/drm/i915/i915_gem_request.h @@ -51,6 +51,13 @@ struct intel_signal_node { * emission time to be associated with the request for tracking how far ahead * of the GPU the submission is. * + * When modifying this structure be very aware that we perform a lockless + * RCU lookup of it that may race against reallocation of the struct + * from the slab freelist. We intentionally do not zero the structure on + * allocation so that the lookup can use the dangling pointers (and is + * cogniscent that those pointers may be wrong). Instead, everything that + * needs to be initialised must be done so explicitly. + * * The requests are reference counted. */ struct drm_i915_gem_request { @@ -111,7 +118,7 @@ struct drm_i915_gem_request { /** Batch buffer related to this request if any (used for * error state dump only). */ - struct drm_i915_gem_object *batch_obj; + struct i915_vma *batch; struct list_head active_list; /** Time at which this request was emitted, in jiffies. */ @@ -127,9 +134,6 @@ struct drm_i915_gem_request { /** file_priv list entry for this request */ struct list_head client_list; - /** process identifier submitting this request */ - struct pid *pid; - /** * The ELSP only accepts two elements at a time, so we queue * context/tail pairs on a given queue (ring->execlist_queue) until the @@ -218,13 +222,11 @@ static inline void i915_gem_request_assign(struct drm_i915_gem_request **pdst, *pdst = src; } -void __i915_add_request(struct drm_i915_gem_request *req, - struct drm_i915_gem_object *batch_obj, - bool flush_caches); +void __i915_add_request(struct drm_i915_gem_request *req, bool flush_caches); #define i915_add_request(req) \ - __i915_add_request(req, NULL, true) + __i915_add_request(req, true) #define i915_add_request_no_flush(req) \ - __i915_add_request(req, NULL, false) + __i915_add_request(req, false) struct intel_rps_client; #define NO_WAITBOOST ERR_PTR(-1) @@ -360,41 +362,34 @@ __i915_gem_active_peek(const struct i915_gem_active *active) } /** - * i915_gem_active_peek - report the active request being monitored + * i915_gem_active_raw - return the active request * @active - the active tracker * - * i915_gem_active_peek() returns the current request being tracked if - * still active, or NULL. It does not obtain a reference on the request - * for the caller, so the caller must hold struct_mutex. + * i915_gem_active_raw() returns the current request being tracked, or NULL. + * It does not obtain a reference on the request for the caller, so the caller + * must hold struct_mutex. */ static inline struct drm_i915_gem_request * -i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex) +i915_gem_active_raw(const struct i915_gem_active *active, struct mutex *mutex) { - struct drm_i915_gem_request *request; - - request = rcu_dereference_protected(active->request, - lockdep_is_held(mutex)); - if (!request || i915_gem_request_completed(request)) - return NULL; - - return request; + return rcu_dereference_protected(active->request, + lockdep_is_held(mutex)); } /** - * i915_gem_active_peek_rcu - report the active request being monitored + * i915_gem_active_peek - report the active request being monitored * @active - the active tracker * - * i915_gem_active_peek_rcu() returns the current request being tracked if + * i915_gem_active_peek() returns the current request being tracked if * still active, or NULL. It does not obtain a reference on the request - * for the caller, and inspection of the request is only valid under - * the RCU lock. + * for the caller, so the caller must hold struct_mutex. */ static inline struct drm_i915_gem_request * -i915_gem_active_peek_rcu(const struct i915_gem_active *active) +i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex) { struct drm_i915_gem_request *request; - request = rcu_dereference(active->request); + request = i915_gem_active_raw(active, mutex); if (!request || i915_gem_request_completed(request)) return NULL; @@ -465,6 +460,10 @@ __i915_gem_active_get_rcu(const struct i915_gem_active *active) * just report the active tracker is idle. If the new request is * incomplete, then we acquire a reference on it and check that * it remained the active request. + * + * It is then imperative that we do not zero the request on + * reallocation, so that we can chase the dangling pointers! + * See i915_gem_request_alloc(). */ do { struct drm_i915_gem_request *request; @@ -497,6 +496,9 @@ __i915_gem_active_get_rcu(const struct i915_gem_active *active) * incremented) then the following read for rcu_access_pointer() * must occur after the atomic operation and so confirm * that this request is the one currently being tracked. + * + * The corresponding write barrier is part of + * rcu_assign_pointer(). */ if (!request || request == rcu_access_pointer(active->request)) return rcu_pointer_handoff(request); @@ -635,8 +637,7 @@ i915_gem_active_retire(struct i915_gem_active *active, struct drm_i915_gem_request *request; int ret; - request = rcu_dereference_protected(active->request, - lockdep_is_held(mutex)); + request = i915_gem_active_raw(active, mutex); if (!request) return 0; |
