exec_ctx.h

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/*
 *
 * Copyright 2015 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_EXEC_CTX_H
#define GRPC_CORE_LIB_IOMGR_EXEC_CTX_H
 
#include <grpc/support/port_platform.h>
 
#include <limits>
 
#include <grpc/impl/codegen/gpr_types.h>
#include <grpc/impl/codegen/grpc_types.h>
#include <grpc/support/atm.h>
#include <grpc/support/cpu.h>
#include <grpc/support/log.h>
 
#include "src/core/lib/gpr/time_precise.h"
#include "src/core/lib/gpr/tls.h"
#include "src/core/lib/gprpp/debug_location.h"
#include "src/core/lib/gprpp/fork.h"
#include "src/core/lib/gprpp/time.h"
#include "src/core/lib/iomgr/closure.h"
 
typedef struct grpc_combiner grpc_combiner;
 
/* This exec_ctx is ready to return: either pre-populated, or cached as soon as
   the finish_check returns true */
#define GRPC_EXEC_CTX_FLAG_IS_FINISHED 1
/* The exec_ctx's thread is (potentially) owned by a call or channel: care
   should be given to not delete said call/channel from this exec_ctx */
#define GRPC_EXEC_CTX_FLAG_THREAD_RESOURCE_LOOP 2
/* This exec ctx was initialized by an internal thread, and should not
   be counted by fork handlers */
#define GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD 4
 
/* This application callback exec ctx was initialized by an internal thread, and
   should not be counted by fork handlers */
#define GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD 1
 
namespace grpc_core {
class Combiner;
class ExecCtx {
 public:
  ExecCtx() : flags_(GRPC_EXEC_CTX_FLAG_IS_FINISHED) {
    Fork::IncExecCtxCount();
    Set(this);
  }
 
  explicit ExecCtx(uintptr_t fl) : flags_(fl) {
    if (!(GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
      Fork::IncExecCtxCount();
    }
    Set(this);
  }
 
  virtual ~ExecCtx() {
    flags_ |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
    Flush();
    Set(last_exec_ctx_);
    if (!(GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
      Fork::DecExecCtxCount();
    }
  }
 
  ExecCtx(const ExecCtx&) = delete;
  ExecCtx& operator=(const ExecCtx&) = delete;
 
  unsigned starting_cpu() {
    if (starting_cpu_ == std::numeric_limits<unsigned>::max()) {
      starting_cpu_ = gpr_cpu_current_cpu();
    }
    return starting_cpu_;
  }
 
  struct CombinerData {
    /* currently active combiner: updated only via combiner.c */
    Combiner* active_combiner;
    /* last active combiner in the active combiner list */
    Combiner* last_combiner;
  };
 
  CombinerData* combiner_data() { return &combiner_data_; }
 
  grpc_closure_list* closure_list() { return &closure_list_; }
 
  uintptr_t flags() { return flags_; }
 
  bool HasWork() {
    return combiner_data_.active_combiner != nullptr ||
           !grpc_closure_list_empty(closure_list_);
  }
 
  bool Flush();
 
  bool IsReadyToFinish() {
    if ((flags_ & GRPC_EXEC_CTX_FLAG_IS_FINISHED) == 0) {
      if (CheckReadyToFinish()) {
        flags_ |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
        return true;
      }
      return false;
    } else {
      return true;
    }
  }
 
  Timestamp Now();
 
  void InvalidateNow() { now_is_valid_ = false; }
 
  void SetNowIomgrShutdown() {
    now_ = Timestamp::InfFuture();
    now_is_valid_ = true;
  }
 
  void TestOnlySetNow(Timestamp new_val) {
    now_ = new_val;
    now_is_valid_ = true;
  }
 
  static ExecCtx* Get() { return exec_ctx_; }
 
  static void Run(const DebugLocation& location, grpc_closure* closure,
                  grpc_error_handle error);
 
  static void RunList(const DebugLocation& location, grpc_closure_list* list);
 
 protected:
  virtual bool CheckReadyToFinish() { return false; }
 
  static void operator delete(void* /* p */) { abort(); }
 
 private:
  static void Set(ExecCtx* exec_ctx) { exec_ctx_ = exec_ctx; }
 
  grpc_closure_list closure_list_ = GRPC_CLOSURE_LIST_INIT;
  CombinerData combiner_data_ = {nullptr, nullptr};
  uintptr_t flags_;
 
  unsigned starting_cpu_ = std::numeric_limits<unsigned>::max();
 
  bool now_is_valid_ = false;
  Timestamp now_;
 
  static GPR_THREAD_LOCAL(ExecCtx*) exec_ctx_;
  ExecCtx* last_exec_ctx_ = Get();
};
 
class ApplicationCallbackExecCtx {
 public:
  ApplicationCallbackExecCtx() { Set(this, flags_); }
 
  explicit ApplicationCallbackExecCtx(uintptr_t fl) : flags_(fl) {
    Set(this, flags_);
  }
 
  ~ApplicationCallbackExecCtx() {
    if (Get() == this) {
      while (head_ != nullptr) {
        auto* f = head_;
        head_ = f->internal_next;
        if (f->internal_next == nullptr) {
          tail_ = nullptr;
        }
        (*f->functor_run)(f, f->internal_success);
      }
      callback_exec_ctx_ = nullptr;
      if (!(GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
        Fork::DecExecCtxCount();
      }
    } else {
      GPR_DEBUG_ASSERT(head_ == nullptr);
      GPR_DEBUG_ASSERT(tail_ == nullptr);
    }
  }
 
  uintptr_t Flags() { return flags_; }
 
  static ApplicationCallbackExecCtx* Get() { return callback_exec_ctx_; }
 
  static void Set(ApplicationCallbackExecCtx* exec_ctx, uintptr_t flags) {
    if (Get() == nullptr) {
      if (!(GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags)) {
        Fork::IncExecCtxCount();
      }
      callback_exec_ctx_ = exec_ctx;
    }
  }
 
  static void Enqueue(grpc_completion_queue_functor* functor, int is_success) {
    functor->internal_success = is_success;
    functor->internal_next = nullptr;
 
    ApplicationCallbackExecCtx* ctx = Get();
 
    if (ctx->head_ == nullptr) {
      ctx->head_ = functor;
    }
    if (ctx->tail_ != nullptr) {
      ctx->tail_->internal_next = functor;
    }
    ctx->tail_ = functor;
  }
 
  static void GlobalInit(void) {}
 
  static void GlobalShutdown(void) {}
 
  static bool Available() { return Get() != nullptr; }
 
 private:
  uintptr_t flags_{0u};
  grpc_completion_queue_functor* head_{nullptr};
  grpc_completion_queue_functor* tail_{nullptr};
  static GPR_THREAD_LOCAL(ApplicationCallbackExecCtx*) callback_exec_ctx_;
};
 
}  // namespace grpc_core
 
#endif /* GRPC_CORE_LIB_IOMGR_EXEC_CTX_H */