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 <grpc/fork.h>
30 #include <grpc/grpc.h>
31 #include <string.h>
32
33 #include "absl/log/log.h"
34 #include "src/core/lib/iomgr/ev_posix.h"
35 #include "src/core/lib/iomgr/executor.h"
36 #include "src/core/lib/iomgr/timer_manager.h"
37 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
38 #include "src/core/lib/surface/init_internally.h"
39 #include "src/core/util/crash.h"
40 #include "src/core/util/fork.h"
41 #include "src/core/util/thd.h"
42
43 //
44 // NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK
45 // AROUND VERY SPECIFIC USE CASES.
46 //
47
48 namespace {
49 bool skipped_handler = true;
50 bool registered_handlers = false;
51 } // namespace
52
grpc_prefork()53 void grpc_prefork() {
54 skipped_handler = true;
55 // This may be called after core shuts down, so verify initialized before
56 // instantiating an ExecCtx.
57 if (!grpc_core::IsInitializedInternally()) {
58 return;
59 }
60 grpc_core::ExecCtx exec_ctx;
61 if (!grpc_core::Fork::Enabled()) {
62 LOG(ERROR) << "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 LOG(INFO) << "Fork support is only compatible with the epoll1 and poll "
71 "polling strategies";
72 return;
73 }
74 if (!grpc_core::Fork::BlockExecCtx()) {
75 LOG(INFO) << "Other threads are currently calling into gRPC, skipping "
76 "fork() handlers";
77 return;
78 }
79 grpc_timer_manager_set_threading(false);
80 grpc_core::Executor::SetThreadingAll(false);
81 grpc_core::ExecCtx::Get()->Flush();
82 grpc_core::Fork::AwaitThreads();
83 skipped_handler = false;
84 }
85
grpc_postfork_parent()86 void grpc_postfork_parent() {
87 if (!skipped_handler) {
88 grpc_core::Fork::AllowExecCtx();
89 grpc_core::ExecCtx exec_ctx;
90 grpc_timer_manager_set_threading(true);
91 grpc_core::Executor::SetThreadingAll(true);
92 }
93 }
94
grpc_postfork_child()95 void grpc_postfork_child() {
96 if (!skipped_handler) {
97 grpc_core::Fork::AllowExecCtx();
98 grpc_core::ExecCtx exec_ctx;
99 for (auto* reset_polling_engine :
100 grpc_core::Fork::GetResetChildPollingEngineFunc()) {
101 if (reset_polling_engine != nullptr) {
102 reset_polling_engine();
103 }
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