[Bug nptl/12403] New: futex issues with --enable-kernel=2.6.22 to 2.6.28

[Bug nptl/12403] New: futex issues with --enable-kernel=2.6.22 to 2.6.28

[allan at archlinux dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

           Summary: futex issues with --enable-kernel=2.6.22 to 2.6.28
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: allan@archlinux.org
              Host: x86_64-unknown-linux-gnu


When building glibc on x86_64 linux with --enable-kernel set for 2.6.22 to
2.6.28 inclusive, the following tests fail:

make[2]: *** [/build/glibc-build/nptl/tst-rwlock6.out] Error 1
make[2]: *** [/build/glibc-build/nptl/tst-rwlock7.out] Error 1
make[2]: *** [/build/glibc-build/nptl/tst-rwlock9.out] Error 1
make[2]: *** [/build/glibc-build/nptl/tst-rwlock11.out] Error 1
make[2]: *** [/build/glibc-build/nptl/tst-rwlock12.out] Error 11
make[2]: *** [/build/glibc-build/nptl/tst-rwlock14.out] Error 1
make[2]: *** [/build/glibc-build/nptl/tst-abstime.out] Error 1

This issue also results in crashes in various real-world applications.

Looking at what is enabled at the failure boundaries indicates a futex issue:
Support for private futexes was added in 2.6.22
Support for the FUTEX_CLOCK_REALTIME flag was added in 2.6.29

Confirming this is an issue with futex support, glibc built with one of the bad
values for --enable-kernel (2.6.27) and manually adjusting the following
defines:

1 - default - 2.6.22 - 2.6.28:
  # define __ASSUME_PRIVATE_FUTEX    1
  # undef __ASSUME_FUTEX_CLOCK_REALTIME
Glibc tests fail.

2 - default pre 2.6.22:
  # undef __ASSUME_PRIVATE_FUTEX
  # undef __ASSUME_FUTEX_CLOCK_REALTIME
Glibc tests pass.

3 - default 2.6.29 and later:
  # define __ASSUME_PRIVATE_FUTEX    1
  # define __ASSUME_FUTEX_CLOCK_REALTIME    1
Glibc tests pass.

This issues does not occur on i686-pc-linux-gnu.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[allan at archlinux dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #1 from Allan McRae <allan at archlinux dot org> 2011-01-16 09:53:22 UTC ---
Naively trying to locate the source of this bug...  Generating a list of files
that have #ifdef/#ifndef on the __ASSUME_PRIVATE_FUTEX and
__ASSUME_FUTEX_CLOCK_REALTIME defines (assuming this is not some more complex
interaction) and are x86_64 specific (as this does not occur on i686 builds)
gives:

nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
nptl/sysdeps/unix/sysv/linux/x86_64/lowlevelrobustlock.S
nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S
nptl/sysdeps/unix/sysv/linux/x86_64/pthread_rwlock_timedrdlock.S
nptl/sysdeps/unix/sysv/linux/x86_64/pthread_rwlock_timedwrlock.S

If we further assume that the bug requires a nested #ifdef for these two
values, that restricts the issue to small parts of the last three files and
given the test suite failures we can exclude the first of those.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Ulrich Drepper <drepper.fsp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #2 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-01-16 16:03:22 UTC ---
This is no place to report such problems.

*** This bug has been marked as a duplicate of bug 333 ***

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[allan at archlinux dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #3 from Allan McRae <allan at archlinux dot org> 2011-01-16 22:50:05 UTC ---
I have shown the issue occurs on a specific platform and with specific values
for --enable-kernel and shown it is a specific combination of defines that
results in the issue.

I would have thought that specific enough to be able to replicate the issue and
for it not to be a #333 duplicate. What further information is needed to show
this is a genuine glibc issue?

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[bz-glibc at kdzbn dot homelinux.net]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #4 from Bryan Kadzban <bz-glibc at kdzbn dot homelinux.net> 2011-01-23 22:37:14 UTC ---
Created attachment 5208
  --> http://sourceware.org/bugzilla/attachment.cgi?id=5208
Fix stack imbalance under --assume-kernel=2.6.{22..29} in rwlock code

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[bz-glibc at kdzbn dot homelinux.net]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Bryan Kadzban <bz-glibc at kdzbn dot homelinux.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bz-glibc at kdzbn dot
                   |                            |homelinux.net

--- Comment #5 from Bryan Kadzban <bz-glibc at kdzbn dot homelinux.net> 2011-01-23 22:38:12 UTC ---
I'm seeing this as well.  I've tracked it down to a bug in the cleanup code in
pthread_rwlock_timedwrlock.S (causing a stack imbalance just before "retq") --
it uses __ASSUME_PRIVATE_FUTEX when deciding whether or not to clean up after
the local variables (and saved register) created for
__ASSUME_FUTEX_CLOCK_REALTIME.  When these two are set differently, "retq"
jumps off into never-never-land.

There's a related bug in pthread_rwlock_timedrdlock.S, which emits the wrong
CFI directives, but I don't think this will affect runtime.  (Could be wrong
though; I don't know a lot about CFI.)

Attached is a patch that fixes both issues; with this, all crashing in the
testsuite is gone.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[allan at archlinux dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Allan McRae <allan at archlinux dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|DUPLICATE                   |

--- Comment #6 from Allan McRae <allan at archlinux dot org> 2011-01-24 05:17:46 UTC ---
Thanks. I can confirm that patch fixes the issues I was observing.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[vapier at gentoo dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Mike Frysinger <vapier at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |toolchain at gentoo dot org

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[j at bitron dot ch]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Jürg Billeter <j at bitron dot ch> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |j at bitron dot ch

--- Comment #7 from Jürg Billeter <j at bitron dot ch> 2011-07-25 09:43:57 UTC ---
I've just spent some time debugging a crash in asterisk which I tracked down to
the issue described here; my patch looks identical. Is there any reason why
this is not yet in master (and at least 2.13 and 2.14).

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[schwab@linux-m68k.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl.tools at gmail dot com

--- Comment #8 from Andreas Schwab <schwab@linux-m68k.org> 2011-08-18 06:51:58 UTC ---
*** Bug 13106 has been marked as a duplicate of this bug. ***

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

Ulrich Drepper <drepper.fsp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #9 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-09-09 03:55:40 UTC ---
I checked in a patch.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[vapier at gentoo dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #10 from Mike Frysinger <vapier at gentoo dot org> 2012-01-09 19:39:22 UTC ---
guess only one site needed updating:

http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=1e4bd093e664f2889c48e63714583ef06b90d5b9

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[bz-glibc at kdzbn dot homelinux.net]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #11 from Bryan Kadzban <bz-glibc at kdzbn dot homelinux.net> 2012-01-10 07:11:17 UTC ---
> guess only one site needed updating:

Sort of.  Only one site affects the generated machine code (and that site was
fixed in the git change that you linked to), but git head still has broken CFI
data at the other site.

Which may or may not be an actual problem, depending on what happens.  If the
kernel tries to trace back into userspace from one of the other syscalls, the
info still might be totally broken.  But at least the code works now, which is
a step up from before.  I'm not very hopeful about the CFI data *ever* getting
fixed, unfortunately.  :-/

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[vapier at gentoo dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=12403

--- Comment #12 from Mike Frysinger <vapier at gentoo dot org> 2012-01-10 21:03:52 UTC ---
that sounds like a diff (if semi-related) bug.  could you file a new one for us
to track it ?

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[jackie.rosen at hushmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=12403

Jackie Rosen <jackie.rosen at hushmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jackie.rosen at hushmail dot com

--- Comment #13 from Jackie Rosen <jackie.rosen at hushmail dot com> ---
*** Bug 260998 has been marked as a duplicate of this bug. ***
Seen from the domain http://volichat.com
Page where seen: http://volichat.com/adult-chat-rooms
Marked for reference. Resolved as fixed @bugzilla.

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[schwab at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=12403

Andreas Schwab <schwab at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|jackie.rosen at hushmail dot com   |

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[Bug nptl/12403] futex issues with --enable-kernel=2.6.22 to 2.6.28

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=12403

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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