| /* |
| * |
| * 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. |
| * |
| */ |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include "src/core/lib/gprpp/fork.h" |
| |
| #include <string.h> |
| |
| #include <grpc/support/alloc.h> |
| #include <grpc/support/sync.h> |
| #include <grpc/support/time.h> |
| |
| #include "src/core/lib/gpr/env.h" |
| #include "src/core/lib/gpr/useful.h" |
| #include "src/core/lib/gprpp/memory.h" |
| |
| /* |
| * NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK |
| * AROUND VERY SPECIFIC USE CASES. |
| */ |
| |
| namespace grpc_core { |
| namespace internal { |
| // The exec_ctx_count has 2 modes, blocked and unblocked. |
| // When unblocked, the count is 2-indexed; exec_ctx_count=2 indicates |
| // 0 active ExecCtxs, exex_ctx_count=3 indicates 1 active ExecCtxs... |
| |
| // When blocked, the exec_ctx_count is 0-indexed. Note that ExecCtx |
| // creation can only be blocked if there is exactly 1 outstanding ExecCtx, |
| // meaning that BLOCKED and UNBLOCKED counts partition the integers |
| #define UNBLOCKED(n) (n + 2) |
| #define BLOCKED(n) (n) |
| |
| class ExecCtxState { |
| public: |
| ExecCtxState() : fork_complete_(true) { |
| gpr_mu_init(&mu_); |
| gpr_cv_init(&cv_); |
| gpr_atm_no_barrier_store(&count_, UNBLOCKED(0)); |
| } |
| |
| void IncExecCtxCount() { |
| gpr_atm count = gpr_atm_no_barrier_load(&count_); |
| while (true) { |
| if (count <= BLOCKED(1)) { |
| // This only occurs if we are trying to fork. Wait until the fork() |
| // operation completes before allowing new ExecCtxs. |
| gpr_mu_lock(&mu_); |
| if (gpr_atm_no_barrier_load(&count_) <= BLOCKED(1)) { |
| while (!fork_complete_) { |
| gpr_cv_wait(&cv_, &mu_, gpr_inf_future(GPR_CLOCK_REALTIME)); |
| } |
| } |
| gpr_mu_unlock(&mu_); |
| } else if (gpr_atm_no_barrier_cas(&count_, count, count + 1)) { |
| break; |
| } |
| count = gpr_atm_no_barrier_load(&count_); |
| } |
| } |
| |
| void DecExecCtxCount() { gpr_atm_no_barrier_fetch_add(&count_, -1); } |
| |
| bool BlockExecCtx() { |
| // Assumes there is an active ExecCtx when this function is called |
| if (gpr_atm_no_barrier_cas(&count_, UNBLOCKED(1), BLOCKED(1))) { |
| gpr_mu_lock(&mu_); |
| fork_complete_ = false; |
| gpr_mu_unlock(&mu_); |
| return true; |
| } |
| return false; |
| } |
| |
| void AllowExecCtx() { |
| gpr_mu_lock(&mu_); |
| gpr_atm_no_barrier_store(&count_, UNBLOCKED(0)); |
| fork_complete_ = true; |
| gpr_cv_broadcast(&cv_); |
| gpr_mu_unlock(&mu_); |
| } |
| |
| ~ExecCtxState() { |
| gpr_mu_destroy(&mu_); |
| gpr_cv_destroy(&cv_); |
| } |
| |
| private: |
| bool fork_complete_; |
| gpr_mu mu_; |
| gpr_cv cv_; |
| gpr_atm count_; |
| }; |
| |
| class ThreadState { |
| public: |
| ThreadState() : awaiting_threads_(false), threads_done_(false), count_(0) { |
| gpr_mu_init(&mu_); |
| gpr_cv_init(&cv_); |
| } |
| |
| void IncThreadCount() { |
| gpr_mu_lock(&mu_); |
| count_++; |
| gpr_mu_unlock(&mu_); |
| } |
| |
| void DecThreadCount() { |
| gpr_mu_lock(&mu_); |
| count_--; |
| if (awaiting_threads_ && count_ == 0) { |
| threads_done_ = true; |
| gpr_cv_signal(&cv_); |
| } |
| gpr_mu_unlock(&mu_); |
| } |
| void AwaitThreads() { |
| gpr_mu_lock(&mu_); |
| awaiting_threads_ = true; |
| threads_done_ = (count_ == 0); |
| while (!threads_done_) { |
| gpr_cv_wait(&cv_, &mu_, gpr_inf_future(GPR_CLOCK_REALTIME)); |
| } |
| awaiting_threads_ = true; |
| gpr_mu_unlock(&mu_); |
| } |
| |
| ~ThreadState() { |
| gpr_mu_destroy(&mu_); |
| gpr_cv_destroy(&cv_); |
| } |
| |
| private: |
| bool awaiting_threads_; |
| bool threads_done_; |
| gpr_mu mu_; |
| gpr_cv cv_; |
| int count_; |
| }; |
| |
| } // namespace |
| |
| void Fork::GlobalInit() { |
| if (!override_enabled_) { |
| #ifdef GRPC_ENABLE_FORK_SUPPORT |
| support_enabled_ = true; |
| #else |
| support_enabled_ = false; |
| #endif |
| bool env_var_set = false; |
| char* env = gpr_getenv("GRPC_ENABLE_FORK_SUPPORT"); |
| if (env != nullptr) { |
| static const char* truthy[] = {"yes", "Yes", "YES", "true", |
| "True", "TRUE", "1"}; |
| static const char* falsey[] = {"no", "No", "NO", "false", |
| "False", "FALSE", "0"}; |
| for (size_t i = 0; i < GPR_ARRAY_SIZE(truthy); i++) { |
| if (0 == strcmp(env, truthy[i])) { |
| support_enabled_ = true; |
| env_var_set = true; |
| break; |
| } |
| } |
| if (!env_var_set) { |
| for (size_t i = 0; i < GPR_ARRAY_SIZE(falsey); i++) { |
| if (0 == strcmp(env, falsey[i])) { |
| support_enabled_ = false; |
| env_var_set = true; |
| break; |
| } |
| } |
| } |
| gpr_free(env); |
| } |
| } |
| if (support_enabled_) { |
| exec_ctx_state_ = grpc_core::New<internal::ExecCtxState>(); |
| thread_state_ = grpc_core::New<internal::ThreadState>(); |
| } |
| } |
| |
| void Fork::GlobalShutdown() { |
| if (support_enabled_) { |
| grpc_core::Delete(exec_ctx_state_); |
| grpc_core::Delete(thread_state_); |
| } |
| } |
| |
| bool Fork::Enabled() { return support_enabled_; } |
| |
| // Testing Only |
| void Fork::Enable(bool enable) { |
| override_enabled_ = true; |
| support_enabled_ = enable; |
| } |
| |
| void Fork::IncExecCtxCount() { |
| if (support_enabled_) { |
| exec_ctx_state_->IncExecCtxCount(); |
| } |
| } |
| |
| void Fork::DecExecCtxCount() { |
| if (support_enabled_) { |
| exec_ctx_state_->DecExecCtxCount(); |
| } |
| } |
| |
| void Fork::SetResetChildPollingEngineFunc( |
| Fork::child_postfork_func reset_child_polling_engine) { |
| reset_child_polling_engine_ = reset_child_polling_engine; |
| } |
| Fork::child_postfork_func Fork::GetResetChildPollingEngineFunc() { |
| return reset_child_polling_engine_; |
| } |
| |
| bool Fork::BlockExecCtx() { |
| if (support_enabled_) { |
| return exec_ctx_state_->BlockExecCtx(); |
| } |
| return false; |
| } |
| |
| void Fork::AllowExecCtx() { |
| if (support_enabled_) { |
| exec_ctx_state_->AllowExecCtx(); |
| } |
| } |
| |
| void Fork::IncThreadCount() { |
| if (support_enabled_) { |
| thread_state_->IncThreadCount(); |
| } |
| } |
| |
| void Fork::DecThreadCount() { |
| if (support_enabled_) { |
| thread_state_->DecThreadCount(); |
| } |
| } |
| void Fork::AwaitThreads() { |
| if (support_enabled_) { |
| thread_state_->AwaitThreads(); |
| } |
| } |
| |
| internal::ExecCtxState* Fork::exec_ctx_state_ = nullptr; |
| internal::ThreadState* Fork::thread_state_ = nullptr; |
| bool Fork::support_enabled_ = false; |
| bool Fork::override_enabled_ = false; |
| Fork::child_postfork_func Fork::reset_child_polling_engine_ = nullptr; |
| } // namespace grpc_core |