GNU C Library master sources branch release/2.22/master updated. glibc-2.22-29-gcd51b14

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Thu Dec 17 17:18:00 GMT 2015


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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=cd51b1424477652cccdb83e7a95644d198fd4513

commit cd51b1424477652cccdb83e7a95644d198fd4513
Author: Paul Murphy <murphyp@linux.vnet.ibm.com>
Date:   Thu Aug 27 09:48:04 2015 -0500

    powerpc: Fix usage of elision transient failure adapt param
    
    The skip_lock_out_of_tbegin_retries adaptive parameter was
    not being used correctly, nor as described.  This prevents
    a fallback for all users of the lock if a transient abort
    occurs within the accepted number of retries.
    
    	[BZ #19174]
    	* sysdeps/powerpc/nptl/elide.h (__elide_lock): Fix usage of
    	.skip_lock_out_of_tbegin_retries.
    	* sysdeps/unix/sysv/linux/powerpc/elision-lock.c
    	(__lll_lock_elision): Likewise, and respect a value of
    	try_tbegin <= 0.
    
    (cherry picked from commit 72f1463df85a522bfd1568e47bd81371522ee358)
    
    Conflicts:
    	NEWS

diff --git a/ChangeLog b/ChangeLog
index 5c92a3e..d96d6ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2015-12-17  Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
+
+	[BZ #19174]
+	* sysdeps/powerpc/nptl/elide.h (__elide_lock): Fix usage of
+	.skip_lock_out_of_tbegin_retries.
+	* sysdeps/unix/sysv/linux/powerpc/elision-lock.c
+	(__lll_lock_elision): Likewise, and respect a value of
+	try_tbegin <= 0.
+
 2015-12-03  Andrew Senkevich  <andrew.senkevich@intel.com>
 
 	* math/Makefile ($(inst_libdir)/libm.so): Corrected path to
diff --git a/NEWS b/NEWS
index e100318..e1c1e58 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.22.1
 * The following bugs are resolved with this release:
 
   18589, 18743, 18778, 18781, 18787, 18796, 18870, 18887, 18921, 18928,
-  18969, 19018, 19058, 19178.
+  18969, 19018, 19058, 19174, 19178.
 
 * The LD_POINTER_GUARD environment variable can no longer be used to
   disable the pointer guard feature.  It is always enabled.
diff --git a/sysdeps/powerpc/nptl/elide.h b/sysdeps/powerpc/nptl/elide.h
index 12171f4..2e1e443 100644
--- a/sysdeps/powerpc/nptl/elide.h
+++ b/sysdeps/powerpc/nptl/elide.h
@@ -27,7 +27,7 @@
    configurations.  Returns true if the system should retry again or false
    otherwise.  */
 static inline bool
-__get_new_count (uint8_t *adapt_count)
+__get_new_count (uint8_t *adapt_count, int attempt)
 {
   /* A persistent failure indicates that a retry will probably
      result in another failure.  Use normal locking now and
@@ -40,7 +40,7 @@ __get_new_count (uint8_t *adapt_count)
     }
   /* Same logic as above, but for a number of temporary failures in a
      a row.  */
-  else if (__elision_aconf.skip_lock_out_of_tbegin_retries > 0
+  else if (attempt <= 1 && __elision_aconf.skip_lock_out_of_tbegin_retries > 0
 	   && __elision_aconf.try_tbegin > 0)
     *adapt_count = __elision_aconf.skip_lock_out_of_tbegin_retries;
   return true;
@@ -78,7 +78,7 @@ __get_new_count (uint8_t *adapt_count)
 	      __builtin_tabort (_ABORT_LOCK_BUSY);			\
 	    }								\
 	  else								\
-	    if (!__get_new_count(&adapt_count))				\
+	    if (!__get_new_count (&adapt_count,i))			\
 	      break;							\
 	}								\
     ret;								\
diff --git a/sysdeps/unix/sysv/linux/powerpc/elision-lock.c b/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
index 7f9bcc2..c6731ca 100644
--- a/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
+++ b/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
@@ -72,8 +72,7 @@ __lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared)
       goto use_lock;
     }
 
-  int try_begin = aconf.try_tbegin;
-  while (1)
+  for (int i = aconf.try_tbegin; i > 0; i--)
     {
       if (__builtin_tbegin (0))
 	{
@@ -87,21 +86,19 @@ __lll_lock_elision (int *lock, short *adapt_count, EXTRAARG int pshared)
 	  /* A persistent failure indicates that a retry will probably
 	     result in another failure.  Use normal locking now and
 	     for the next couple of calls.  */
-	  if (try_begin-- <= 0
-	      || _TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
+	  if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
 	    {
 	      if (aconf.skip_lock_internal_abort > 0)
 		*adapt_count = aconf.skip_lock_internal_abort;
 	      goto use_lock;
 	    }
-	  /* Same logic as above, but for for a number of temporary failures
-	     in a row.  */
-	  else if (aconf.skip_lock_out_of_tbegin_retries > 0
-                   && aconf.try_tbegin > 0)
-	    *adapt_count = aconf.skip_lock_out_of_tbegin_retries;
 	}
      }
 
+  /* Fall back to locks for a bit if retries have been exhausted */
+  if (aconf.try_tbegin > 0 && aconf.skip_lock_out_of_tbegin_retries > 0)
+    *adapt_count = aconf.skip_lock_out_of_tbegin_retries;
+
 use_lock:
   return LLL_LOCK ((*lock), pshared);
 }

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                      |    9 +++++++++
 NEWS                                           |    2 +-
 sysdeps/powerpc/nptl/elide.h                   |    6 +++---
 sysdeps/unix/sysv/linux/powerpc/elision-lock.c |   15 ++++++---------
 4 files changed, 19 insertions(+), 13 deletions(-)


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