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/*
* Phusion Passenger - https://www.phusionpassenger.com/
* Copyright (c) 2010-2017 Phusion Holding B.V.
*
* "Passenger", "Phusion Passenger" and "Union Station" are registered
* trademarks of Phusion Holding B.V.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef _PASSENGER_PROCESS_MANAGEMENT_UTILS_H_
#define _PASSENGER_PROCESS_MANAGEMENT_UTILS_H_
#include <sys/types.h>
namespace Passenger {
using namespace std;
/**
* Thread-safe and async-signal safe way to fork().
*
* On Linux, the fork() glibc wrapper grabs a ptmalloc lock, so
* if malloc causes a segfault then we can't fork.
* http://sourceware.org/bugzilla/show_bug.cgi?id=4737
*
* OS X apparently does something similar, except they use a
* spinlock so it results in 100% CPU. See _cthread_fork_prepare()
* at http://www.opensource.apple.com/source/Libc/Libc-166/threads.subproj/cthreads.c
* However, since POSIX in OS X is implemented on top of a Mach layer,
* calling asyncFork() can mess up the state of the Mach layer, causing
* some POSIX functions to mysteriously fail. See
* https://code.google.com/p/phusion-passenger/issues/detail?id=1094
* You should therefore not use asyncFork() unless you're in a signal
* handler or if you only perform async-signal-safe stuff in the child.
*
* On 2017 October 9 with macOS 10.11 El Capitan, we also confirmed
* a case in which the child process can get stuck indefinitely with 0% CPU.
* If we we create a thread which performs memory allocation, and shortly
* after thread creation we fork, then the child process gets stuck because
* one of its pthread_atfork() handlers tries to allocate memory, which tries
* to grab a lock which was already locked. This means that on macOS
* we pretty much can never use regular fork() at all in a multithreaded
* environment.
*
* As of 2018 May 16 with macOS 10.13 High Sierra, it was confirmed that the
* use of asyncFork() can lead to the following messages to be printed
* if the child process allocates memory:
*
* malloc: *** mach_vm_map(size=1048576) failed (error code=268435459)
* malloc: *** error: can't allocate region securely
* malloc: *** set a breakpoint in malloc_error_break to debug
*
* See https://github.com/phusion/passenger/issues/1193#issuecomment-389503928
*/
pid_t asyncFork();
/**
* Resets the current process's signal handler disposition and signal mask
* to default values. One should call this every time one forks a child process;
* non-default signal masks/handler dispositions can cause all kinds of weird quirks,
* like waitpid() malfunctioning on macOS.
*
* This function is async-signal safe.
*/
void resetSignalHandlersAndMask();
/**
* Disables malloc() debugging facilities on macOS.
*/
void disableMallocDebugging();
/**
* Close all file descriptors that are higher than `lastToKeepOpen`.
*
* If you set `asyncSignalSafe` to true, then this function becomes fully async-signal,
* through the use of asyncFork() instead of fork(). However, read the documentation
* for asyncFork() to learn about its caveats.
*
* Also, regardless of whether `asyncSignalSafe` is true or not, this function is not
* *thread* safe. Make sure there are no other threads running that might open file
* descriptors, otherwise some file descriptors might not be closed even though they
* should be.
*/
void closeAllFileDescriptors(int lastToKeepOpen, bool asyncSignalSafe = false);
/**
* Given a failed exec() syscall and its resulting errno
* value, print an appropriate error message to STDERR.
*
* This function is async signal-safe. Its main intended use is to be the
* default value for the `onExecFail` parameter for the
* `runCommand()` and `runCommandAndCaptureOutput()` functions.
*/
void printExecError(const char **command, int errcode);
void printExecError2(const char **command, int errcode, char *buf, size_t size);
} // namespace Passenger
#endif /* _PASSENGER_PROCESS_MANAGEMENT_UTILS_H_ */
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