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POSpawn process from multithreaded application
 

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    <p>I have a situation where I need to spawn a helper process from within a very large, multithreaded application, which I do not have complete control over.</p> <p>Right now I'm using <code>fork()</code>/<code>exec()</code>. This works a lot of the time, but in some circumstances the child crashes weirdly before the <code>exec()</code> happens. I'm suspecting this is because <code>fork()</code>ing multithreaded applications is generally considered to be a Really Bad Idea.</p> <p>I would really, really like a way to start a process atomically, without <code>fork()</code>ing the parent: with all file descriptors closed, environment set up the way I want, CWD set, etc. This should avoid all the horror of <code>fork()</code>ing my multithreaded parent app, and dealing with file descriptor inheritance, etc. <code>posix_spawn()</code> should be ideal. Unfortunately, on Linux, <code>posix_spawn()</code> is implemented using <code>fork()</code> and <code>exec()</code>...</p> <p><code>vfork()</code> is defined to suspend the parent process until the child calls <code>exec()</code>. This would appear to be more like what I want, but my understanding was that <code>vfork()</code> is generally considered a historical relic these days and is equivalent to <code>fork()</code> --- is this still the case?</p> <p>What's the least bad way of dealing with this?</p> <p>Note that: </p> <ul> <li>I cannot spawn my process before any threads start (because I can't run code at that point)</li> <li>I cannot redesign my application not to need the helper process, due to external requirements</li> <li>I cannot suspend all my threads before spawning the helper process, because they don't belong to me</li> </ul> <p>This is on Linux. Java is involved, but all <em>my</em> code is in C.</p>
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    1. COSince you're already using threads, why not just start a new thread that calls `system()` and runs whatever it is you need?
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      1. USBrian Roach
    2. COThere's no inherent problem with fork() in a multithreaded program, bar it might be a tad inefficient for large memory hungry and busy threaded applicatons.
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    3. COsystem() works by doing fork()/exec()!
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