[Bug nptl/13184] New: rwlocks can go into dead lock

["redhat at pureftpd dot org" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13184

             Bug #: 13184
           Summary: rwlocks can go into dead lock
           Product: glibc
           Version: 2.14
            Status: NEW
          Severity: critical
          Priority: P2
         Component: nptl
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: redhat@pureftpd.org
    Classification: Unclassified


This issue can be reliably reproduced on glibc 2.7, glibc 2.11, glibc 1.14 and
glibc-current (stock, without any vendor patches).

A race condition can cause a pthreads rwlock to get a negative number of
__nr_readers, thus leading to a dead lock.

This issue seems to be hardware dependent. I haven't been able to reproduce it
on single-core Opterons nor Intel hardware. But it happens in minutes on
different boxes, all powered by dual-core Opteron 270.

A test program triggering this issue can be found at:
http://download.pureftpd.org/misc/nptl-bugs/crazylock.c

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