[issue11284] slow close file descriptors in subprocess, popen2, os.popen*

[Charles-Francois Natali]

Charles-Francois Natali <neologix at free.fr> added the comment:

> Your posix_closefrom() implementation as written today is not safe to call between fork() and exec() due to the opendir/readdir implementation.  It can and will hang processes at unexpected times.

Yeah, I remove the patch when I realized that.

> According to http://www.unix.com/man-page/All/3c/closefrom/ closefrom() is not async-signal-safe. :(

Strange. I was sure closefrom was implemented with fcntl.

> I still want to find a way to do this nicely on Linux (even if it means me going and implementing a closefrom syscall to be added to 2.6.39).

Well, arguably, CLOEXEC is designed to cope with this kind of situation.
closefrom is more like a hack (and mostly useless if it's really not async-safe).

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