[Bug c++/61538] g++ compiled binary, linked to glibc libpthread, hangs on SGI MIPS R1x000 systems on Linux

["kumba at gentoo dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61538

--- Comment #14 from Joshua Kinard <kumba at gentoo dot org> ---
(In reply to Andrew Pinski from comment #13)
> What is the kernel version?  There has been some recent (this year) fixes
> inside the kernel for futex.
> 
> Though I admit I have seen this just recently when debugging a program where
> I did next over a pthread_mutex_unlock call.

Was under 3.14.x.  I already tried going back to 3.14.0, due to the recent
futex security flaws covered in CVE-2014-3153.  Now on 3.15.5 on the Octane,
and my test binaries still hang, so I've pretty much ruled out it being the
kernel.

I've been doing a git bisect of gcc the last few days, and I've pinned the
problem commit down to somewhere between Jun 12 2012 and June 26 2012. 
anything prior to the 26th works so far, anything after doesn't.  My current
bisect build is going to test June 19 2012 next.  Averages about ~7.5hrs for
gcc and 3.5hrs for glibc to build, so I can cram in roughly, 2 tests a day.

So far, I am leaning towards commit 30c3c4427521f96fb58b6e1debb86da4f113f06f as
the culprit.  That was added on June 20th, and I *think* the refactoring of the
case statement is wrong for MIPS.  The logic just doesn't seem to work out to
be the same as the old code it replaced, and maybe this only is a problem on
the R10000 processors.  So if my build for June 19 2012 works, then a another
'git bisect good' should put me somewhere between the 23rd/24th, and if that's
bad, I'm going to then try to test a gcc checkout both with and without that
one commit to verify if it's the bug or not.

https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=30c3c4427521f96fb58b6e1debb86da4f113f06f