Remove support for lock elision.

The support for lock elision was already deprecated with glibc 2.42:
commit 77438db8cfa6ee66b3906230156bdae11c49a195
"Mark support for lock elision as deprecated."
See also discussions:
https://sourceware.org/pipermail/libc-alpha/2025-July/168492.html

This patch removes the architecture specific support for lock elision
for x86, powerpc and s390 by removing the elision-conf.h, elision-conf.c,
elision-lock.c, elision-timed.c, elision-unlock.c, elide.h, htm.h/hle.h files.
Those generic files are also removed.

The architecture specific structures are adjusted and the elision fields are
marked as unused.  See struct_mutex.h files.
Furthermore in struct_rwlock.h, the leftover __rwelision was also removed.
Those were originally removed with commit 0377a7fde6dfcc078dda29a1225d7720a0931357
"nptl: Remove rwlock elision definitions"
and by chance reintroduced with commit 7df8af43ad1cd8ce527444de50bee6f35eebe071
"nptl: Add struct_rwlock.h"

The common code (e.g. the pthread_mutex-files) are changed back to the time
before lock elision was introduced with the x86-support:
- commit 1cdbe579482c07e9f4bb3baa4864da2d3e7eb837
"Add the low level infrastructure for pthreads lock elision with TSX"
- commit b023e4ca99f5e81f90d87d23cd267ef2abd2388c
"Add new internal mutex type flags for elision."
- commit 68cc29355f3334c7ad18f648ff9a6383a0916d23
"Add minimal test suite changes for elision enabled kernels"
- commit e8c659d74e011346785355eeef03b7fb6f533c61
"Add elision to pthread_mutex_{try,timed,un}lock"
- commit 49186d21ef2d87986bccaf0a7c45c48c91b265f3
"Disable elision for any pthread_mutexattr_settype call"
- commit 1717da59aed9612becd56aaa1249aac695af4c8a
"Add a configure option to enable lock elision and disable by default"

Elision is removed also from the tunables, the initialization part, the
pretty-printers and the manual.

Some extra handling in the testsuite is removed as well as the full tst-mutex10
testcase, which tested a race while enabling lock elision.

I've also searched the code for "elision", "elide", "transaction" and e.g.
cleaned some comments.

I've run the testsuite on x86_64 and s390x and run the build-many-glibcs.py
script.
Thanks to Sachin Monga, this patch is also tested on powerpc.

A NEWS entry also mentions the removal.
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

1 files changed, 5 insertions, 6 deletions

diff --git a/sysdeps/s390/nptl/bits/struct_mutex.h b/sysdeps/s390/nptl/bits/struct_mutex.h
index af0e2e997e..5bc66d4a1e 100644
--- a/sysdeps/s390/nptl/bits/struct_mutex.h
+++ b/sysdeps/s390/nptl/bits/struct_mutex.h
@@ -32,7 +32,7 @@ struct __pthread_mutex_s
   int __kind;
 #if __WORDSIZE == 64
   short __spins;
-  short __elision;
+  short __unused;
   __pthread_list_t __list;
 # define __PTHREAD_MUTEX_HAVE_PREV      1
 #else
@@ -41,11 +41,10 @@ struct __pthread_mutex_s
   {
     struct
     {
-      short __espins;
-      short __elision;
-    } _d;
-#  define __spins _d.__espins
-#  define __elision _d.__elision
+      short __data_spins;
+      short __data_unused;
+    } __data;
+#  define __spins __data.__data_spins
     __pthread_slist_t __list;
   };
 # define __PTHREAD_MUTEX_HAVE_PREV      0