File powerpc-elision-adapt-param.patch of Package glibc.4896

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File powerpc-elision-adapt-param.patch of Package glibc.4896

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.

Index: glibc-2.22/sysdeps/powerpc/nptl/elide.h
===================================================================
--- glibc-2.22.orig/sysdeps/powerpc/nptl/elide.h
+++ glibc-2.22/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;								\
Index: glibc-2.22/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
===================================================================
--- glibc-2.22.orig/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
+++ glibc-2.22/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
@@ -72,8 +72,7 @@ __lll_lock_elision (int *lock, short *ad
       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 *ad
 	  /* 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);
 }

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File powerpc-elision-adapt-param.patch of Package glibc.4896

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