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From: "robert at ocallahan dot org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/17208] New: pthread_cond_wait may put mutex into incorrect state if mutex has elision disabled
Date: Mon, 28 Jul 2014 06:41:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=17208

            Bug ID: 17208
           Summary: pthread_cond_wait may put mutex into incorrect state
                    if mutex has elision disabled
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: robert at ocallahan dot org
                CC: drepper.fsp at gmail dot com

pthread_cond_wait calls __pthread_mutex_cond_lock_adjust after acquiring the
mutex's futex. __pthread_mutex_cond_lock_adjust has the following code:
  if (mutex->__data.__kind == PTHREAD_MUTEX_PI_RECURSIVE_NP)
    ++mutex->__data.__count;
I think this code should check PTHREAD_MUTEX_TYPE(mutex->__data.__kind).
Otherwise, if the mutex is recursive but __kind has the
PTHREAD_MUTEX_ELISION_NP or PTHREAD_MUTEX_NO_ELISION_NP, __count will not be
incremented and a later pthread_mutex_unlock of the mutex goes wrong,
decrementing __count from 0 to 0xffffffff and failing to unlock the mutex.

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