| /* |
| * |
| * Copyright 2017 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| #ifndef GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H |
| #define GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include <stddef.h> |
| |
| #include <grpc/support/atm.h> |
| |
| #include "src/core/lib/gpr/mpscq.h" |
| #include "src/core/lib/gprpp/inlined_vector.h" |
| #include "src/core/lib/gprpp/ref_counted.h" |
| #include "src/core/lib/gprpp/ref_counted_ptr.h" |
| #include "src/core/lib/iomgr/closure.h" |
| #include "src/core/lib/iomgr/dynamic_annotations.h" |
| |
| // A simple, lock-free mechanism for serializing activity related to a |
| // single call. This is similar to a combiner but is more lightweight. |
| // |
| // It requires the callback (or, in the common case where the callback |
| // actually kicks off a chain of callbacks, the last callback in that |
| // chain) to explicitly indicate (by calling GRPC_CALL_COMBINER_STOP()) |
| // when it is done with the action that was kicked off by the original |
| // callback. |
| |
| extern grpc_core::TraceFlag grpc_call_combiner_trace; |
| |
| struct grpc_call_combiner { |
| gpr_atm size = 0; // size_t, num closures in queue or currently executing |
| gpr_mpscq queue; |
| // Either 0 (if not cancelled and no cancellation closure set), |
| // a grpc_closure* (if the lowest bit is 0), |
| // or a grpc_error* (if the lowest bit is 1). |
| gpr_atm cancel_state = 0; |
| #ifdef GRPC_TSAN_ENABLED |
| // A fake ref-counted lock that is kept alive after the destruction of |
| // grpc_call_combiner, when we are running the original closure. |
| // |
| // Ideally we want to lock and unlock the call combiner as a pointer, when the |
| // callback is called. However, original_closure is free to trigger |
| // anything on the call combiner (including destruction of grpc_call). |
| // Thus, we need a ref-counted structure that can outlive the call combiner. |
| struct TsanLock |
| : public grpc_core::RefCounted<TsanLock, |
| grpc_core::NonPolymorphicRefCount> { |
| TsanLock() { TSAN_ANNOTATE_RWLOCK_CREATE(&taken); } |
| ~TsanLock() { TSAN_ANNOTATE_RWLOCK_DESTROY(&taken); } |
| |
| // To avoid double-locking by the same thread, we should acquire/release |
| // the lock only when taken is false. On each acquire taken must be set to |
| // true. |
| std::atomic<bool> taken{false}; |
| }; |
| grpc_core::RefCountedPtr<TsanLock> tsan_lock = |
| grpc_core::MakeRefCounted<TsanLock>(); |
| grpc_closure tsan_closure; |
| grpc_closure* original_closure; |
| #endif |
| }; |
| |
| // Assumes memory was initialized to zero. |
| void grpc_call_combiner_init(grpc_call_combiner* call_combiner); |
| |
| void grpc_call_combiner_destroy(grpc_call_combiner* call_combiner); |
| |
| #ifndef NDEBUG |
| #define GRPC_CALL_COMBINER_START(call_combiner, closure, error, reason) \ |
| grpc_call_combiner_start((call_combiner), (closure), (error), __FILE__, \ |
| __LINE__, (reason)) |
| #define GRPC_CALL_COMBINER_STOP(call_combiner, reason) \ |
| grpc_call_combiner_stop((call_combiner), __FILE__, __LINE__, (reason)) |
| /// Starts processing \a closure on \a call_combiner. |
| void grpc_call_combiner_start(grpc_call_combiner* call_combiner, |
| grpc_closure* closure, grpc_error* error, |
| const char* file, int line, const char* reason); |
| /// Yields the call combiner to the next closure in the queue, if any. |
| void grpc_call_combiner_stop(grpc_call_combiner* call_combiner, |
| const char* file, int line, const char* reason); |
| #else |
| #define GRPC_CALL_COMBINER_START(call_combiner, closure, error, reason) \ |
| grpc_call_combiner_start((call_combiner), (closure), (error), (reason)) |
| #define GRPC_CALL_COMBINER_STOP(call_combiner, reason) \ |
| grpc_call_combiner_stop((call_combiner), (reason)) |
| /// Starts processing \a closure on \a call_combiner. |
| void grpc_call_combiner_start(grpc_call_combiner* call_combiner, |
| grpc_closure* closure, grpc_error* error, |
| const char* reason); |
| /// Yields the call combiner to the next closure in the queue, if any. |
| void grpc_call_combiner_stop(grpc_call_combiner* call_combiner, |
| const char* reason); |
| #endif |
| |
| /// Registers \a closure to be invoked by \a call_combiner when |
| /// grpc_call_combiner_cancel() is called. |
| /// |
| /// Once a closure is registered, it will always be scheduled exactly |
| /// once; this allows the closure to hold references that will be freed |
| /// regardless of whether or not the call was cancelled. If a cancellation |
| /// does occur, the closure will be scheduled with the cancellation error; |
| /// otherwise, it will be scheduled with GRPC_ERROR_NONE. |
| /// |
| /// The closure will be scheduled in the following cases: |
| /// - If grpc_call_combiner_cancel() was called prior to registering the |
| /// closure, it will be scheduled immediately with the cancelation error. |
| /// - If grpc_call_combiner_cancel() is called after registering the |
| /// closure, the closure will be scheduled with the cancellation error. |
| /// - If grpc_call_combiner_set_notify_on_cancel() is called again to |
| /// register a new cancellation closure, the previous cancellation |
| /// closure will be scheduled with GRPC_ERROR_NONE. |
| /// |
| /// If \a closure is NULL, then no closure will be invoked on |
| /// cancellation; this effectively unregisters the previously set closure. |
| /// However, most filters will not need to explicitly unregister their |
| /// callbacks, as this is done automatically when the call is destroyed. Filters |
| /// that schedule the cancellation closure on ExecCtx do not need to take a ref |
| /// on the call stack to guarantee closure liveness. This is done by explicitly |
| /// flushing ExecCtx after the unregistration during call destruction. |
| void grpc_call_combiner_set_notify_on_cancel(grpc_call_combiner* call_combiner, |
| grpc_closure* closure); |
| |
| /// Indicates that the call has been cancelled. |
| void grpc_call_combiner_cancel(grpc_call_combiner* call_combiner, |
| grpc_error* error); |
| |
| namespace grpc_core { |
| |
| // Helper for running a list of closures in a call combiner. |
| // |
| // Each callback running in the call combiner will eventually be |
| // returned to the surface, at which point the surface will yield the |
| // call combiner. So when we are running in the call combiner and have |
| // more than one callback to return to the surface, we need to re-enter |
| // the call combiner for all but one of those callbacks. |
| class CallCombinerClosureList { |
| public: |
| CallCombinerClosureList() {} |
| |
| // Adds a closure to the list. The closure must eventually result in |
| // the call combiner being yielded. |
| void Add(grpc_closure* closure, grpc_error* error, const char* reason) { |
| closures_.emplace_back(closure, error, reason); |
| } |
| |
| // Runs all closures in the call combiner and yields the call combiner. |
| // |
| // All but one of the closures in the list will be scheduled via |
| // GRPC_CALL_COMBINER_START(), and the remaining closure will be |
| // scheduled via GRPC_CLOSURE_SCHED(), which will eventually result in |
| // yielding the call combiner. If the list is empty, then the call |
| // combiner will be yielded immediately. |
| void RunClosures(grpc_call_combiner* call_combiner) { |
| if (closures_.empty()) { |
| GRPC_CALL_COMBINER_STOP(call_combiner, "no closures to schedule"); |
| return; |
| } |
| for (size_t i = 1; i < closures_.size(); ++i) { |
| auto& closure = closures_[i]; |
| GRPC_CALL_COMBINER_START(call_combiner, closure.closure, closure.error, |
| closure.reason); |
| } |
| if (grpc_call_combiner_trace.enabled()) { |
| gpr_log(GPR_INFO, |
| "CallCombinerClosureList executing closure while already " |
| "holding call_combiner %p: closure=%p error=%s reason=%s", |
| call_combiner, closures_[0].closure, |
| grpc_error_string(closures_[0].error), closures_[0].reason); |
| } |
| // This will release the call combiner. |
| GRPC_CLOSURE_SCHED(closures_[0].closure, closures_[0].error); |
| closures_.clear(); |
| } |
| |
| // Runs all closures in the call combiner, but does NOT yield the call |
| // combiner. All closures will be scheduled via GRPC_CALL_COMBINER_START(). |
| void RunClosuresWithoutYielding(grpc_call_combiner* call_combiner) { |
| for (size_t i = 0; i < closures_.size(); ++i) { |
| auto& closure = closures_[i]; |
| GRPC_CALL_COMBINER_START(call_combiner, closure.closure, closure.error, |
| closure.reason); |
| } |
| closures_.clear(); |
| } |
| |
| size_t size() const { return closures_.size(); } |
| |
| private: |
| struct CallCombinerClosure { |
| grpc_closure* closure; |
| grpc_error* error; |
| const char* reason; |
| |
| CallCombinerClosure(grpc_closure* closure, grpc_error* error, |
| const char* reason) |
| : closure(closure), error(error), reason(reason) {} |
| }; |
| |
| // There are generally a maximum of 6 closures to run in the call |
| // combiner, one for each pending op. |
| InlinedVector<CallCombinerClosure, 6> closures_; |
| }; |
| |
| } // namespace grpc_core |
| |
| #endif /* GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H */ |