[PATCH 2/6] Fall back to locking if elision runs out of retries.

[Dominik Vogt <vogt at linux dot vnet dot ibm dot com>]

With the old code, elision would never be disabled if every transaction aborts
with a temporary failure.  This patch introduces a new configuration value that
is used whenever pthread_mutex_lock runs out of retries.

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany

>From 433efb398303d42acfe7c859ed4c62d8df9d306d Mon Sep 17 00:00:00 2001
From: Dominik Vogt <vogt@de.ibm.com>
Date: Mon, 2 Sep 2013 06:56:13 +0000
Subject: [PATCH 2/7] x86: Fall back to locking if elision runs out of
 retries.

With the old code, elision would never be disabled if every transaction aborts
with a temporary failure.
---
 nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c | 3 +++
 nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h | 1 +
 nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c | 4 ++++
 3 files changed, 8 insertions(+)

diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
index 2fed32b..c6bd49f 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.c
@@ -35,6 +35,9 @@ struct elision_config __elision_aconf =
        to reasons other than other threads' memory accesses.  Expressed in
        number of lock acquisition attempts.  */
     .skip_lock_internal_abort = 3,
+    /* How often to not attempt to use elision if a lock used up all retries
+       without success.  Expressed in number of lock acquisition attempts.  */
+    .skip_lock_out_of_retries = 3,
     /* How often we retry using elision if there is chance for the transaction
        to finish execution (e.g., it wasn't aborted due to the lock being
        already acquired.  */
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
index 02cd2a6..1e519e9 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-conf.h
@@ -28,6 +28,7 @@ struct elision_config
 {
   int skip_lock_busy;
   int skip_lock_internal_abort;
+  int skip_lock_out_of_retries;
   int retry_try_xbegin;
   int skip_trylock_internal_abort;
 };
diff --git a/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c b/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
index 45370ed..04f7c28 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
+++ b/nptl/sysdeps/unix/sysv/linux/x86/elision-lock.c
@@ -82,6 +82,10 @@ __lll_lock_elision (int *futex, short *adapt_count, EXTRAARG int private)
 	      break;
 	    }
 	}
+      /* Same logic as above, but for for a number of tepmorary failures in a
+	 row.  */
+      if (aconf.skip_lock_out_of_retries > 0 && aconf.retry_try_xbegin > 0)
+	*adapt_count = aconf.skip_lock_out_of_retries;
     }
   else
     {
-- 
1.7.11.4