https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=557e7cf22612e3a9e2d8abe032c0c57a39029ad3
commit 557e7cf22612e3a9e2d8abe032c0c57a39029ad3
Author: Radek Bartoň <radek.bar...@microsoft.com>
Date: Thu Jun 5 12:41:37 2025 +0200
Cygwin: implement spinlock pause for AArch64
Signed-off-by: Radek Bartoň <radek.bar...@microsoft.com>
Diff:
---
winsup/cygwin/local_includes/cygtls.h | 5 ++++-
winsup/cygwin/thread.cc | 5 +++++
winsup/testsuite/winsup.api/pthread/cpu_relax.h | 3 ++-
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/winsup/cygwin/local_includes/cygtls.h
b/winsup/cygwin/local_includes/cygtls.h
index 29a539d83..44bd44e72 100644
--- a/winsup/cygwin/local_includes/cygtls.h
+++ b/winsup/cygwin/local_includes/cygtls.h
@@ -243,8 +243,11 @@ public: /* Do NOT remove this public: line, it's a marker
for gentls_offsets. */
{
while (InterlockedExchange (&stacklock, 1))
{
-#ifdef __x86_64__
+#if defined(__x86_64__)
__asm__ ("pause");
+#elif defined(__aarch64__)
+ __asm__ ("dmb ishst\n"
+ "yield");
#else
#error unimplemented for this target
#endif
diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
index fea6079b8..510e2be93 100644
--- a/winsup/cygwin/thread.cc
+++ b/winsup/cygwin/thread.cc
@@ -1968,7 +1968,12 @@ pthread_spinlock::lock ()
else if (spins < FAST_SPINS_LIMIT)
{
++spins;
+#if defined(__x86_64__)
__asm__ volatile ("pause":::);
+#elif defined(__aarch64__)
+ __asm__ volatile ("dmb ishst\n"
+ "yield":::);
+#endif
}
else
{
diff --git a/winsup/testsuite/winsup.api/pthread/cpu_relax.h
b/winsup/testsuite/winsup.api/pthread/cpu_relax.h
index 1936dc5f4..71cec0b2b 100644
--- a/winsup/testsuite/winsup.api/pthread/cpu_relax.h
+++ b/winsup/testsuite/winsup.api/pthread/cpu_relax.h
@@ -4,7 +4,8 @@
#if defined(__x86_64__) || defined(__i386__) // Check for x86 architectures
#define CPU_RELAX() __asm__ volatile ("pause" :::)
#elif defined(__aarch64__) || defined(__arm__) // Check for ARM architectures
- #define CPU_RELAX() __asm__ volatile ("yield" :::)
+ #define CPU_RELAX() __asm__ volatile ("dmb ishst \
+ yield" :::)
#else
#error unimplemented for this target
#endif
