7086ad6919
In practice, with this implementation we never need to make a system call. We get the main thread's tid (which is the same as our pid) back from the set_tid_address system call we have to make during initialization. A new pthread will have the same pid as its parent, and a fork child's main (and only) thread will have a pid equal to its tid, which we get for free from the kernel before clone returns. The only time we'd actually have to make a getpid system call now is if we take a signal during fork and the signal handler calls getpid. (That, or we call getpid in the dynamic linker while it's still dealing with its own relocations and hasn't even set up the main thread yet.) Bug: 15387103 Change-Id: I6d4718ed0a5c912fc75b5f738c49a023dbed5189
58 lines
2.2 KiB
C++
58 lines
2.2 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <unistd.h>
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#include <sys/syscall.h>
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#include "pthread_internal.h"
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#define FORK_FLAGS (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD)
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int fork() {
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__bionic_atfork_run_prepare();
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pthread_internal_t* self = __get_thread();
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// Remember the parent pid and invalidate the cached value while we fork.
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pid_t parent_pid = self->invalidate_cached_pid();
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#if defined(__x86_64__) // sys_clone's last two arguments are flipped on x86-64.
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int result = syscall(__NR_clone, FORK_FLAGS, NULL, NULL, &(self->tid), NULL);
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#else
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int result = syscall(__NR_clone, FORK_FLAGS, NULL, NULL, NULL, &(self->tid));
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#endif
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if (result == 0) {
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self->set_cached_pid(gettid());
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__bionic_atfork_run_child();
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} else {
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self->set_cached_pid(parent_pid);
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__bionic_atfork_run_parent();
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}
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return result;
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}
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