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    <p>fork'ing multithreaded application is considered to be safe if you use only async-signal-safe operations. POSIX <a href="http://pubs.opengroup.org/onlinepubs/007904975/functions/fork.html" rel="nofollow">says</a>:</p> <blockquote> <p>A process shall be created with a single thread. If a multi-threaded process calls fork(), the new process shall contain a replica of the calling thread and its entire address space, possibly including the states of mutexes and other resources. Consequently, to avoid errors, the child process may only execute async-signal-safe operations until such time as one of the exec functions is called. Fork handlers may be established by means of the pthread_atfork() function in order to maintain application invariants across fork() calls.</p> </blockquote> <p>posix_spawn() is not the best idea:</p> <blockquote> <p>It is also complicated to modify the environment of a multi-threaded process temporarily, since all threads must agree when it is safe for the environment to be changed. However, this cost is only borne by those invocations of posix_spawn() and posix_spawnp() that use the additional functionality. Since extensive modifications are not the usual case, and are particularly unlikely in time-critical code, keeping much of the environment control out of posix_spawn() and posix_spawnp() is appropriate design. </p> </blockquote> <p>(see <a href="http://linux.die.net/man/3/posix_spawn" rel="nofollow">man posix_spawn</a>)</p> <p>I guess you have problems with replicated from parent resources. You may clean them up using pthread_atfork() handler (you use pthread, right?). The other way is to use low level function for process creation called <a href="http://www.kernel.org/doc/man-pages/online/pages/man2/clone.2.html" rel="nofollow">clone()</a>. It gives you almost full control on what exactly child process should inherit from its parent.</p> <p><strong>[UPDATE]</strong></p> <p>Probably the simplest way to get rid of the problem is to change your fork'ing scheme. For example you can create a new process (fork) even before your program initializes all resources. I.e. call fork() in main() before you create all your threads. In child process setup a signal handler (for example for SIGUSR2 signal) and sleep. When parent needs to exec some new process, it sends the SIGUSR2 signal to your child process. When child catches it, it calls fork/exec.</p>
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    1. POSpawn process from multithreaded application
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    1. USDan Kruchinin
    1. USDan Kruchinin
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      1. VTUpMod
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    1. COYou can use `>` to write quotes. I edited your post :)
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      1. USShahbaz
    2. CO@Shahbaz heh, it seems you updated it at the same time I did and your changes wasn't saved (fixed).
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      1. USDan Kruchinin
    3. COThanks, but if you look at my question you'll see that I explicitly say that I *can't* create my new process before the threads start. If you want the messy details, it's because my code runs as a dynamically loaded JNI object, and Java's already created a hundred threads before my code even loads...
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      1. USDavid Given
 

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