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native: Use WNOHANG before signaling #13131

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merged 1 commit into from
Mar 28, 2014
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alexcrichton
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It turns out that on linux, and possibly other platforms, child processes will
continue to accept signals until they have been reaped. This means that once
the child has exited, it will succeed to receive signals until waitpid() has
been invoked on it.

This is unfortunate behavior, and differs from what is seen on OSX and windows.
This commit changes the behavior of Process::signal() to be the same across
platforms, and updates the documentation of Process::kill() to note that when
signaling a foreign process it may accept signals until reaped.

Implementation-wise, this invokes waitpid() with WNOHANG before each signal to
the child to ensure that if the child has exited that we will reap it. Other
possibilities include installing a SIGCHLD signal handler, but at this time I
believe that that's too complicated.

Closes #13124

@japaric
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japaric commented Mar 26, 2014

This solves #13124, but issue #13123 is still present.

It turns out that on linux, and possibly other platforms, child processes will
continue to accept signals until they have been *reaped*. This means that once
the child has exited, it will succeed to receive signals until waitpid() has
been invoked on it.

This is unfortunate behavior, and differs from what is seen on OSX and windows.
This commit changes the behavior of Process::signal() to be the same across
platforms, and updates the documentation of Process::kill() to note that when
signaling a foreign process it may accept signals until reaped.

Implementation-wise, this invokes waitpid() with WNOHANG before each signal to
the child to ensure that if the child has exited that we will reap it. Other
possibilities include installing a SIGCHLD signal handler, but at this time I
believe that that's too complicated.

Closes rust-lang#13124
bors added a commit that referenced this pull request Mar 28, 2014
It turns out that on linux, and possibly other platforms, child processes will
continue to accept signals until they have been *reaped*. This means that once
the child has exited, it will succeed to receive signals until waitpid() has
been invoked on it.

This is unfortunate behavior, and differs from what is seen on OSX and windows.
This commit changes the behavior of Process::signal() to be the same across
platforms, and updates the documentation of Process::kill() to note that when
signaling a foreign process it may accept signals until reaped.

Implementation-wise, this invokes waitpid() with WNOHANG before each signal to
the child to ensure that if the child has exited that we will reap it. Other
possibilities include installing a SIGCHLD signal handler, but at this time I
believe that that's too complicated.

Closes #13124
@bors bors closed this Mar 28, 2014
@bors bors merged commit 0e190b9 into rust-lang:master Mar 28, 2014
@alexcrichton alexcrichton deleted the issue-13124 branch March 28, 2014 21:46
flip1995 pushed a commit to flip1995/rust that referenced this pull request Jul 25, 2024
…lexendoo

Reduce typo count.

changelog: none
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Process::signal(0) returns Ok() when child process was killed externally
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