[Bug nptl/14477] New: Cancelling phtread_cond_wait() hangs with PRIO_INHERIT mutex

["sonicwavezor at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14477

             Bug #: 14477
           Summary: Cancelling phtread_cond_wait() hangs with PRIO_INHERIT
                    mutex
           Product: glibc
           Version: 2.14
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
        AssignedTo: unassigned@sourceware.org
        ReportedBy: sonicwavezor@gmail.com
                CC: drepper.fsp@gmail.com
    Classification: Unclassified


Created attachment 6581
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6581
Test case

I have a problem canceling threads waiting in a pthread_cond_wait(), that use
mutexes with the `PTHREAD_PRIO_INHERIT` attribute set. This only happens on
certain platforms though. I've posted this on stackoverflow also
(http://stackoverflow.com/questions/11878445/cancelling-pthread-cond-wait-hangs-with-prio-inherit-mutex
), posted to the libc-help mailing list, and was told to file a bugreport in
here. 

I haven't yet had the chance to try out the newest versions (been using 2.13
and 2.14), but if anyone could give a few hints as to whether this might be
fixed in the current versions (or isn't broken in an older version), I'd be
happy to hear about it!

The attached minimal example demonstrates my problem: (compile with g++
pthread_cond_wait.cpp -lpthread)

Every time I run it, main() hangs on pthread_join(). A gdb backtrace shows the
following:

    Thread 2 (Thread 0xb7d15b70 (LWP 257)):
    #0  0xb7fde430 in __kernel_vsyscall ()
    #1  0xb7fcf362 in __lll_lock_wait () at
../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:142
    #2  0xb7fcc9f9 in __condvar_w_cleanup () at
../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:434
    #3  0x08048fbe in threadFunc (arg=0x0) at /home/pthread_cond_wait.cpp:22
    #4  0xb7fc8ca0 in start_thread (arg=0xb7d15b70) at pthread_create.c:301
    #5  0xb7de73ae in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

    Thread 1 (Thread 0xb7d166d0 (LWP 254)):
    #0  0xb7fde430 in __kernel_vsyscall ()
    #1  0xb7fc9d64 in pthread_join (threadid=3083950960, thread_return=0x0) at
pthread_join.c:89
    #2  0x0804914a in main () at /home/pthread_cond_wait.cpp:41

If PTHREAD_PRIO_INHERIT isn't set on the mutex, everything works as it should,
and the program exits cleanly.


Platforms with problems:

 - Embedded AMD Fusion board, running a [PTXDist][1] based 32-bit Linux
3.2.9-rt16 (with [RTpatch][2] 16). We are using the newest [OSELAS][3] i686
cross toolchain (2011.11.1), using gcc 4.6.2, glibc 2.14.1, binutils 2.21.1a,
kernel 2.6.39.
 - Same board with the 2011.03.1 toolchain also (gcc 4.5.2 / glibc 2.13 /
binutils 2.18 / kernel 2.6.36).

Platforms with no problems:

 - Our own ARM-board, also running a PTXDist Linux (32-bit 2.6.29.6-rt23),
using OSELAS arm-v4t cross toolchain (1.99.3) with gcc 4.3.2 / glibc 2.8 /
binutils 2.18 / kernel 2.6.27.
 - My laptop (Intel Core i7), running 64-bit Ubuntu 11.04 (virtualized / kernel
2.6.38.15-generic), gcc 4.5.2 / eglibc 2.13-0ubuntu13.1 / binutils
2.21.0.20110327.


I have been looking around the net for solutions, and have come across a few
patches that I've tried, but without any effect:

 - [Making the condition variables priority inheritance aware.][4]
 - [Handling EAGAIN from FUTEX_WAIT_REQUEUE_PI][5]




  [1]: http://www.ptxdist.org/software/ptxdist/index_en.html
  [2]: https://rt.wiki.kernel.org/index.php/Main_Page
  [3]: http://www.ptxdist.de/oselas/toolchain/index_en.html
  [4]: http://sourceware.org/bugzilla/show_bug.cgi?id=11588
  [5]:
http://sourceware.org/git/?p=glibc.git;a=commit;h=c5a0802a682dba23f92d47f0
f99775aebfbe2539


Best regards,
Simon Falsig

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