From: Paul Murphy <murphyp@linux.vnet.ibm.com>
Date: Thu, 27 Aug 2015 14:48:04 +0000 (-0500)
Subject: powerpc: Fix usage of elision transient failure adapt param
X-Git-Tag: glibc-2.23~257
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=72f1463df85a522bfd1568e47bd81371522ee358;p=thirdparty%2Fglibc.git

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.
---

diff --git a/ChangeLog b/ChangeLog
index a392a750303..0a70fee9646 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2015-10-27  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.
+
 2015-10-27  Carlos Eduardo Seo  <cseo@linux.vnet.ibm.com>
 
 	* elf/dl-support.c (_dl_aux_init): Added AT_PLATFORM to the case
diff --git a/NEWS b/NEWS
index 1122affd0df..5120ddc24d0 100644
--- a/NEWS
+++ b/NEWS
@@ -21,7 +21,7 @@ Version 2.23
   18970, 18977, 18980, 18981, 18982, 18985, 19003, 19007, 19012, 19016,
   19018, 19032, 19046, 19049, 19050, 19059, 19071, 19074, 19076, 19077,
   19078, 19079, 19085, 19086, 19088, 19094, 19095, 19124, 19125, 19129,
-  19134, 19137, 19156.
+  19134, 19137, 19156, 19174.
 
 * There is now a --disable-timezone-tools configure option for disabling the
   building and installing of the timezone related utilities (zic, zdump, and
diff --git a/sysdeps/powerpc/nptl/elide.h b/sysdeps/powerpc/nptl/elide.h
index 12171f45dc1..2e1e4432789 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 37627323798..4775fcad104 100644
--- a/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
+++ b/sysdeps/unix/sysv/linux/powerpc/elision-lock.c
@@ -50,8 +50,7 @@ __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))
 	{
@@ -65,21 +64,19 @@ __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);
 }