1 /*
2 *
3 * Copyright 2017 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #include <grpc/support/port_platform.h>
20
21 #include "src/core/lib/iomgr/port.h"
22
23 #ifdef GRPC_POSIX_FORK
24
25 #ifdef GRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK
26 #include <pthread.h>
27 #endif
28
29 #include <string.h>
30
31 #include <grpc/fork.h>
32 #include <grpc/grpc.h>
33 #include <grpc/support/log.h>
34
35 #include "src/core/lib/gprpp/fork.h"
36 #include "src/core/lib/gprpp/thd.h"
37 #include "src/core/lib/iomgr/ev_posix.h"
38 #include "src/core/lib/iomgr/executor.h"
39 #include "src/core/lib/iomgr/timer_manager.h"
40 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
41
42 /*
43 * NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK
44 * AROUND VERY SPECIFIC USE CASES.
45 */
46
47 namespace {
48 bool skipped_handler = true;
49 bool registered_handlers = false;
50 } // namespace
51
grpc_prefork()52 void grpc_prefork() {
53 skipped_handler = true;
54 // This may be called after core shuts down, so verify initialized before
55 // instantiating an ExecCtx.
56 if (!grpc_is_initialized()) {
57 return;
58 }
59 grpc_core::ExecCtx exec_ctx;
60 if (!grpc_core::Fork::Enabled()) {
61 gpr_log(GPR_ERROR,
62 "Fork support not enabled; try running with the "
63 "environment variable GRPC_ENABLE_FORK_SUPPORT=1");
64 return;
65 }
66 const char* poll_strategy_name = grpc_get_poll_strategy_name();
67 if (poll_strategy_name == nullptr ||
68 (strcmp(poll_strategy_name, "epoll1") != 0 &&
69 strcmp(poll_strategy_name, "poll") != 0)) {
70 gpr_log(GPR_INFO,
71 "Fork support is only compatible with the epoll1 and poll polling "
72 "strategies");
73 }
74 if (!grpc_core::Fork::BlockExecCtx()) {
75 gpr_log(GPR_INFO,
76 "Other threads are currently calling into gRPC, skipping fork() "
77 "handlers");
78 return;
79 }
80 grpc_timer_manager_set_threading(false);
81 grpc_core::Executor::SetThreadingAll(false);
82 grpc_core::ExecCtx::Get()->Flush();
83 grpc_core::Fork::AwaitThreads();
84 skipped_handler = false;
85 }
86
grpc_postfork_parent()87 void grpc_postfork_parent() {
88 if (!skipped_handler) {
89 grpc_core::Fork::AllowExecCtx();
90 grpc_core::ExecCtx exec_ctx;
91 grpc_timer_manager_set_threading(true);
92 grpc_core::Executor::SetThreadingAll(true);
93 }
94 }
95
grpc_postfork_child()96 void grpc_postfork_child() {
97 if (!skipped_handler) {
98 grpc_core::Fork::AllowExecCtx();
99 grpc_core::ExecCtx exec_ctx;
100 grpc_core::Fork::child_postfork_func reset_polling_engine =
101 grpc_core::Fork::GetResetChildPollingEngineFunc();
102 if (reset_polling_engine != nullptr) {
103 reset_polling_engine();
104 }
105 grpc_timer_manager_set_threading(true);
106 grpc_core::Executor::SetThreadingAll(true);
107 }
108 }
109
grpc_fork_handlers_auto_register()110 void grpc_fork_handlers_auto_register() {
111 if (grpc_core::Fork::Enabled() & !registered_handlers) {
112 #ifdef GRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK
113 pthread_atfork(grpc_prefork, grpc_postfork_parent, grpc_postfork_child);
114 registered_handlers = true;
115 #endif // GRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK
116 }
117 }
118
119 #endif // GRPC_POSIX_FORK
120