commit 49186d21ef2d87986bccaf0a7c45c48c91b265f3

Author: Andi Kleen <ak@linux.intel.com>

Date:   Thu Jun 27 11:15:06 2013 -0700

    Disable elision for any pthread_mutexattr_settype call

    PTHREAD_MUTEX_NORMAL requires deadlock for nesting, DEFAULT

    does not. Since glibc uses the same value (0) disable elision

    for any call to pthread_mutexattr_settype() with a 0 value.

    This implies that a program can disable elision by doing

    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL)

    Based on a original proposal by Rich Felker.

Index: glibc-2.17-c758a686/nptl/pthread_mutexattr_settype.c

===================================================================

--- glibc-2.17-c758a686.orig/nptl/pthread_mutexattr_settype.c

+++ glibc-2.17-c758a686/nptl/pthread_mutexattr_settype.c

@@ -30,6 +30,11 @@ __pthread_mutexattr_settype (attr, kind)

   if (kind < PTHREAD_MUTEX_NORMAL || kind > PTHREAD_MUTEX_ADAPTIVE_NP)

     return EINVAL;

+  /* Cannot distinguish between DEFAULT and NORMAL. So any settype

+     call disables elision for now.  */

+  if (kind == PTHREAD_MUTEX_DEFAULT)

+    kind |= PTHREAD_MUTEX_NO_ELISION_NP;

+

   iattr = (struct pthread_mutexattr *) attr;

   iattr->mutexkind = (iattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_BITS) | kind;