glibc: Add single-threaded fast path to rand()

Backport a patch [1] to improve performance of rand() and __random()[2]
by adding a single-threaded fast path.

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=be0cfd848d9ad7378800d6302bc11467cf2b514f
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=32777
(From OE-Core rev: 09e2d663246d7335a9e33dd1a86dfe4630e4489a)

Signed-off-by: Haixiao Yan <haixiao.yan.cn@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit b0ded4df5f2d3bb3319978d1a549c72f5daf238e)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

2 files changed, 48 insertions, 0 deletions

diff --git a/meta/recipes-core/glibc/glibc/0001-stdlib-Add-single-threaded-fast-path-to-rand.patch b/meta/recipes-core/glibc/glibc/0001-stdlib-Add-single-threaded-fast-path-to-rand.patch
new file mode 100644
index 0000000000..736fc51f38
--- /dev/null
+++ b/meta/recipes-core/glibc/glibc/0001-stdlib-Add-single-threaded-fast-path-to-rand.patch
@@ -0,0 +1,47 @@
+From 4f54b0dfc16dbe0df86afccb90e447df5f7f571e Mon Sep 17 00:00:00 2001
+From: Wilco Dijkstra <wilco.dijkstra@arm.com>
+Date: Mon, 18 Mar 2024 15:18:20 +0000
+Subject: [PATCH] stdlib: Add single-threaded fast path to rand()
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Improve performance of rand() and __random() by adding a single-threaded
+fast path.  Bench-random-lock shows about 5x speedup on Neoverse V1.
+
+Upstream-Status: Backport [be0cfd848d9ad7378800d6302bc11467cf2b514f]
+
+Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+Signed-off-by: Haixiao Yan <haixiao.yan.cn@windriver.com>
+---
+ stdlib/random.c | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/stdlib/random.c b/stdlib/random.c
+index 17cc61ba8f55..5d482a857065 100644
+--- a/stdlib/random.c
++++ b/stdlib/random.c
+@@ -51,6 +51,7 @@
+    SUCH DAMAGE.*/
+ 
+ #include <libc-lock.h>
++#include <sys/single_threaded.h>
+ #include <limits.h>
+ #include <stddef.h>
+ #include <stdlib.h>
+@@ -288,6 +289,12 @@ __random (void)
+ {
+   int32_t retval;
+ 
++  if (SINGLE_THREAD_P)
++    {
++      (void) __random_r (&unsafe_state, &retval);
++      return retval;
++    }
++
+   __libc_lock_lock (lock);
+ 
+   (void) __random_r (&unsafe_state, &retval);
+-- 
+2.34.1
+
diff --git a/meta/recipes-core/glibc/glibc_2.41.bb b/meta/recipes-core/glibc/glibc_2.41.bb
index 71b89ac9ff..d707e1a677 100644
--- a/meta/recipes-core/glibc/glibc_2.41.bb
+++ b/meta/recipes-core/glibc/glibc_2.41.bb
@@ -53,6 +53,7 @@ SRC_URI =  "${GLIBC_GIT_URI};branch=${SRCBRANCH};name=glibc \
            file://0021-fix-create-thread-failed-in-unprivileged-process-BZ-.patch \
            file://0022-Avoid-hardcoded-build-time-paths-in-the-output-binar.patch \
            file://0023-tests-Skip-2-qemu-tests-that-can-hang-in-oe-selftest.patch \
+           file://0001-stdlib-Add-single-threaded-fast-path-to-rand.patch \
 "
 S = "${WORKDIR}/git"
 B = "${WORKDIR}/build-${TARGET_SYS}"