From: Andi Kleen <ak@linux.intel.com>
Date: Thu, 27 Jun 2013 18:15:06 +0000 (-0700)
Subject: Disable elision for any pthread_mutexattr_settype call
X-Git-Tag: glibc-2.18~54
X-Git-Url: https://sourceware.org/git/?a=commitdiff_plain;h=49186d21ef2d87986bccaf0a7c45c48c91b265f3;p=glibc.git

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.
---

diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index 7f82b2098a..d32046ee65 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,3 +1,8 @@
+2013-07-02  Andi Kleen  <ak@linux.intel.com>
+
+	* pthread_mutexattr_settype.c (__pthread_mutexattr_settype):
+	  Disable elision for PTHREAD_MUTEX_DEFAULT.
+
 2013-07-02  Andi Kleen  <ak@linux.intel.com>
 	    Hongjiu Lu  <hongjiu.lu@intel.com>
 
diff --git a/nptl/pthread_mutexattr_settype.c b/nptl/pthread_mutexattr_settype.c
index 7b476e95bc..a85cdcb389 100644
--- a/nptl/pthread_mutexattr_settype.c
+++ b/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;