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"fix" a nasty race condition
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10860 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -419,6 +419,9 @@ void IP::writeToChild(void *Buffer, unsigned Size) const {
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void IP::killChild() const {
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assert(ChildPID != 0 && "Child has already been reaped!");
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// If the process terminated on its own accord, closing the pipe file
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// descriptors, we will get here. Check to see if the process has already
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// died in this manner, gracefully.
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int Status = 0;
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int PID;
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do {
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@ -426,7 +429,23 @@ void IP::killChild() const {
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} while (PID < 0 && errno == EINTR);
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if (PID < 0) throw "Error waiting for child to exit!";
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// If the child process was already dead, then it died unexpectedly.
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// Ok, there is a slight race condition here. It's possible that we will find
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// out that the file descriptor closed before waitpid will indicate that the
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// process gracefully died. If we don't know that the process gracefully
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// died, wait a bit and try again. This is pretty nasty.
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if (PID == 0) {
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usleep(10000); // Wait a bit.
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// Try again.
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Status = 0;
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do {
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PID = waitpid(ChildPID, &Status, WNOHANG);
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} while (PID < 0 && errno == EINTR);
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if (PID < 0) throw "Error waiting for child to exit!";
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}
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// If the child process was already dead, then indicate that the process
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// terminated on its own.
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if (PID) {
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assert(PID == ChildPID && "Didn't reap child?");
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ChildPID = 0; // Child has been reaped
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