f6a21bfac5
For some program implementation, the pattern like below, calling
pthread_atfork to register atfork interfaces.
pthread_atfork(&atfork_prepare, &atfork_parent, &atfork_child);
When the program is expected to reopen the shared library's handle
inherited from parent in child process. Maybe, dlclose is called in
atfork_child to release the shared library handle before reopen it.
Then, dlclose will indrectly call _cxa_finalize and finaly call
__unregister_atfork when dso is not NULL.
atfork_child() -> dlclose() -> __on_dlclose()
-> __cxa_finalize() -> __unregister_atfork(dso)
In __unregister_atfork, firstly, it try to hold the g_atfork_list_mutex
lock to operate the g_atfork_list. Due to the registered atfork_child is
executed before resetting g_atfork_list_mutex lock in child, the child
process will be blocked here because of deadlock.
Test: bionic-unit-tests32 --gtest_filter=pthread.pthread_atfork_child_with_dlclose
without the fixing, the test will be timeout.
Change-Id: I35d3001682c836e0955d6d681bc5f9297fad0c7b
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
Signed-off-by: Qiming Shi <qiming.shi@intel.com>
Signed-off-by: Chao Xie <chao.xie@intel.com>
114 lines
4.1 KiB
C++
114 lines
4.1 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <gtest/gtest.h>
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#include <dlfcn.h>
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#include "utils.h"
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static int g_atfork_prepare_calls = 0;
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static void AtForkPrepare1() { g_atfork_prepare_calls = (g_atfork_prepare_calls * 10) + 1; }
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static void AtForkPrepare2() { g_atfork_prepare_calls = (g_atfork_prepare_calls * 10) + 2; }
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static void AtForkPrepare3() { g_atfork_prepare_calls = (g_atfork_prepare_calls * 10) + 3; }
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static void AtForkPrepare4() { g_atfork_prepare_calls = (g_atfork_prepare_calls * 10) + 4; }
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static int g_atfork_parent_calls = 0;
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static void AtForkParent1() { g_atfork_parent_calls = (g_atfork_parent_calls * 10) + 1; }
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static void AtForkParent2() { g_atfork_parent_calls = (g_atfork_parent_calls * 10) + 2; }
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static void AtForkParent3() { g_atfork_parent_calls = (g_atfork_parent_calls * 10) + 3; }
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static void AtForkParent4() { g_atfork_parent_calls = (g_atfork_parent_calls * 10) + 4; }
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static int g_atfork_child_calls = 0;
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static void AtForkChild1() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 1; }
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static void AtForkChild2() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 2; }
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static void AtForkChild3() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 3; }
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static void AtForkChild4() { g_atfork_child_calls = (g_atfork_child_calls * 10) + 4; }
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static void* g_atfork_test_handle = nullptr;
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static void AtForkPrepare() {}
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static void AtForkParent() {}
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static void AtForkChild() { dlclose(g_atfork_test_handle); g_atfork_test_handle = dlopen("libtest_pthread_atfork.so", RTLD_NOW | RTLD_LOCAL); }
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TEST(pthread, pthread_atfork_with_dlclose) {
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ASSERT_EQ(0, pthread_atfork(AtForkPrepare1, AtForkParent1, AtForkChild1));
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void* handle = dlopen("libtest_pthread_atfork.so", RTLD_NOW | RTLD_LOCAL);
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ASSERT_TRUE(handle != nullptr) << dlerror();
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typedef int (*fn_t)(void (*)(void), void (*)(void), void (*)(void));
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fn_t fn = reinterpret_cast<fn_t>(dlsym(handle, "proxy_pthread_atfork"));
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ASSERT_TRUE(fn != nullptr) << dlerror();
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// the library registers 2 additional atfork handlers in a constructor
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ASSERT_EQ(0, fn(AtForkPrepare2, AtForkParent2, AtForkChild2));
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ASSERT_EQ(0, fn(AtForkPrepare3, AtForkParent3, AtForkChild3));
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ASSERT_EQ(0, pthread_atfork(AtForkPrepare4, AtForkParent4, AtForkChild4));
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pid_t pid = fork();
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ASSERT_NE(-1, pid) << strerror(errno);
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if (pid == 0) {
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ASSERT_EQ(1234, g_atfork_child_calls);
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_exit(0);
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}
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ASSERT_EQ(1234, g_atfork_parent_calls);
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ASSERT_EQ(4321, g_atfork_prepare_calls);
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EXPECT_EQ(0, dlclose(handle));
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g_atfork_prepare_calls = g_atfork_parent_calls = g_atfork_child_calls = 0;
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AssertChildExited(pid, 0);
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pid = fork();
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ASSERT_NE(-1, pid) << strerror(errno);
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if (pid == 0) {
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ASSERT_EQ(14, g_atfork_child_calls);
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_exit(0);
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}
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ASSERT_EQ(14, g_atfork_parent_calls);
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ASSERT_EQ(41, g_atfork_prepare_calls);
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AssertChildExited(pid, 0);
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}
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TEST(pthread, pthread_atfork_child_with_dlclose) {
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g_atfork_test_handle = dlopen("libtest_pthread_atfork.so", RTLD_NOW | RTLD_LOCAL);
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ASSERT_TRUE(g_atfork_test_handle != nullptr) << dlerror();
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typedef int (*fn_t)(void (*)(void), void (*)(void), void (*)(void));
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fn_t fn = reinterpret_cast<fn_t>(dlsym(g_atfork_test_handle, "proxy_pthread_atfork"));
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ASSERT_TRUE(fn != nullptr) << dlerror();
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// the library registers 2 additional atfork handlers in a constructor
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ASSERT_EQ(0, pthread_atfork(AtForkPrepare, AtForkParent, AtForkChild));
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pid_t pid = fork();
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ASSERT_NE(-1, pid) << strerror(errno);
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if (pid == 0) {
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_exit(0);
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}
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AssertChildExited(pid, 0);
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EXPECT_EQ(0, dlclose(g_atfork_test_handle));
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g_atfork_test_handle = nullptr;
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}
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