Procfs race condition bug

[Mike Cardwell <linux@lists.grepular.com>]

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I originally posted this two years ago (*) but received no response. I
just had a look and the problem still exists on the 3.14 kernel I am
currently running.

I *think* I've uncovered a race condition bug in procfs. If I attempt to
open a file in /proc/net, eg "/proc/net/tcp" it works fine, but if I
spawn a POSIX thread and attempt to do it from there, it *usually* fails
with a "No such file or directory", but some times succeeds. If I do a
system call inside the thread to look up the thread ID and then open
"/proc/THREADID/net/tcp" instead, it works fine.

There are more details and some example code so you can replicate the
problem on a stack overflow question I asked previously here:
http://stackoverflow.com/questions/11580020/opening-proc-net-tcp-in-c-from-a-posix-thread-fails-most-of-the-time

(*) https://lkml.org/lkml/2012/7/20/331

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