update to glibc-2.28-251.2.src.rpm

Signed-off-by: Zhao Hang <wb-zh951434@alibaba-inc.com>

glibc-RHEL-15696-66.patch

@@ -0,0 +1,51 @@
+From d672a98a1af106bd68deb15576710cd61363f7a6 Mon Sep 17 00:00:00 2001
+From: "H.J. Lu" <hjl.tools@gmail.com>
+Date: Tue, 2 Nov 2021 18:33:07 -0700
+Subject: [PATCH] Add LLL_MUTEX_READ_LOCK [BZ #28537]
+Content-type: text/plain; charset=UTF-8
+
+CAS instruction is expensive.  From the x86 CPU's point of view, getting
+a cache line for writing is more expensive than reading.  See Appendix
+A.2 Spinlock in:
+
+https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/xeon-lock-scaling-analysis-paper.pdf
+
+The full compare and swap will grab the cache line exclusive and cause
+excessive cache line bouncing.
+
+Add LLL_MUTEX_READ_LOCK to do an atomic load and skip CAS in spinlock
+loop if compare may fail to reduce cache line bouncing on contended locks.
+
+Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
+---
+ nptl/pthread_mutex_lock.c | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
+index 60ada70d..eb4d8baa 100644
+--- a/nptl/pthread_mutex_lock.c
++++ b/nptl/pthread_mutex_lock.c
+@@ -56,6 +56,11 @@
+ #define FORCE_ELISION(m, s)
+ #endif
+ 
++#ifndef LLL_MUTEX_READ_LOCK
++# define LLL_MUTEX_READ_LOCK(mutex) \
++  atomic_load_relaxed (&(mutex)->__data.__lock)
++#endif
++
+ static int __pthread_mutex_lock_full (pthread_mutex_t *mutex)
+      __attribute_noinline__;
+ 
+@@ -136,6 +141,8 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
+ 		  break;
+ 		}
+ 	      atomic_spin_nop ();
++	      if (LLL_MUTEX_READ_LOCK (mutex) != 0)
++		continue;
+ 	    }
+ 	  while (LLL_MUTEX_TRYLOCK (mutex) != 0);
+ 
+-- 
+GitLab
+