Review request for 5049299 (original) (raw)

Martin Buchholz martinrb at google.com
Tue Jun 30 23:39:35 UTC 2009

[+libc-alpha]

I just filed glibc bug http://sources.redhat.com/bugzilla/show_bug.cgi?id=10353 Methods for deleting all file descriptors greater than given integer

In the JDK... We close all non-relevant file descriptors in the child instead of relying on having the FD_CLOEXEC bit set properly for every fd in the parent.

The technique of choice appears to be to read /proc/self/fd and close all the fds found therein. That's even portable between linux and solaris!

Martin

On Tue, Jun 30, 2009 at 02:48, Michael McMahon <Michael.McMahon at sun.com>wrote:

Roland McGrath wrote:

But...posixspawn doesn't give you any way to delete all file descriptors and if you try to collect them before spawning, there is a race in a multithreaded program.

This is something you should never want to do. There is notoriously no good way to do it on some systems, where getdtablesize() can return RLIMINFINITY and is not proper to use in a loop. Use FDCLOEXEC when you open the descriptor in the first place. We also need to chdir() before calling exec. And while some descriptors already have FDCLOEXEC set, it's not easy to guarantee this for all of them. - Michael. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.openjdk.java.net/pipermail/core-libs-dev/attachments/20090630/41ee68ab/attachment.html>

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