File nptl-optimize-trylock.patch of Package glibc.42452

From 7b8f497fe4ccac805ac4b20ff64946f0a5bbe4e3 Mon Sep 17 00:00:00 2001
From: Sunil K Pandey <sunil.k.pandey@intel.com>
Date: Tue, 9 Dec 2025 08:57:44 -0800
Subject: [PATCH] nptl: Optimize trylock for high cache contention workloads
 (BZ #33704)

Check lock availability before acquisition to reduce cache line
bouncing.  Significantly improves trylock throughput on multi-core
systems under heavy contention.

Tested on x86_64.

Fixes BZ #33704.

Co-authored-by: Alex M Wells <alex.m.wells@intel.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>
(cherry picked from commit 63716823dbad9482e09972907ae98e9cb00f9b86)
---
 nptl/pthread_mutex_trylock.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
index 9b3a16954d..4ac283414d 100644
--- a/nptl/pthread_mutex_trylock.c
+++ b/nptl/pthread_mutex_trylock.c
@@ -48,7 +48,8 @@ ___pthread_mutex_trylock (pthread_mutex_t *mutex)
 	  return 0;
 	}
 
-      if (lll_trylock (mutex->__data.__lock) == 0)
+      if (atomic_load_relaxed (&(mutex->__data.__lock)) == 0
+	  && lll_trylock (mutex->__data.__lock) == 0)
 	{
 	  /* Record the ownership.  */
 	  mutex->__data.__owner = id;
@@ -71,7 +72,10 @@ ___pthread_mutex_trylock (pthread_mutex_t *mutex)
       /*FALL THROUGH*/
     case PTHREAD_MUTEX_ADAPTIVE_NP:
     case PTHREAD_MUTEX_ERRORCHECK_NP:
-      if (lll_trylock (mutex->__data.__lock) != 0)
+      /* Mutex type is already loaded, lock check overhead should
+         be minimal.  */
+      if (atomic_load_relaxed (&(mutex->__data.__lock)) != 0
+	  || lll_trylock (mutex->__data.__lock) != 0)
 	break;
 
       /* Record the ownership.  */
-- 
2.52.0