From 589d416977977f32fde82cd623a7a876ab1d397c Mon Sep 17 00:00:00 2001
From: Lennox Ho <lennoxhoe@gmail.com>
Date: Tue, 19 Sep 2023 14:53:16 +0800
Subject: [PATCH] Add a more performant SpinLockDelay implementation for
 Windows based on WaitOnAddress and friends

---
 CMakeLists.txt                |  3 +++
 Makefile.am                   |  1 +
 src/base/spinlock_win32-inl.h | 19 ++++++++++++++-----
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 03c9961..e705f01 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -566,6 +566,9 @@ if(MINGW OR MSVC)
   # We also need to tell mingw that sysinfo.cc needs shlwapi.lib.
   # (We do this via a #pragma for msvc, but need to do it here for mingw).
   target_link_libraries(sysinfo shlwapi)
+  # spinlock uses WaitOnAddress et al. We need to link to synchronization.lib
+  # (We also do this via a #pragma for msvc, but need to do it here for mingw).
+  target_link_libraries(spinlock synchronization)
 
 else()
   set(SPINLOCK_INCLUDES src/base/spinlock.h
diff --git a/Makefile.am b/Makefile.am
index 7757c68..14aab68 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -205,6 +205,7 @@ noinst_LTLIBRARIES += libspinlock.la
 libspinlock_la_SOURCES = src/base/spinlock.cc \
                          src/base/spinlock_internal.cc \
                          $(SPINLOCK_INCLUDES)
+libspinlock_la_LIBADD = -lsynchronization
 
 LIBSPINLOCK = libwindows.la libspinlock.la libsysinfo.la liblogging.la
 
diff --git a/src/base/spinlock_win32-inl.h b/src/base/spinlock_win32-inl.h
index d511999..5f76a8b 100644
--- a/src/base/spinlock_win32-inl.h
+++ b/src/base/spinlock_win32-inl.h
@@ -35,19 +35,28 @@
 
 #include <windows.h>
 
+#ifdef _MSC_VER
+#   pragma comment(lib, "Synchronization.lib")
+#endif
+
 namespace base {
 namespace internal {
 
 void SpinLockDelay(std::atomic<int> *w, int32 value, int loop) {
-  if (loop == 0) {
-  } else if (loop == 1) {
-    Sleep(0);
-  } else {
-    Sleep(base::internal::SuggestedDelayNS(loop) / 1000000);
+  if (loop != 0) {
+    auto wait_ns = static_cast<uint64_t>(base::internal::SuggestedDelayNS(loop)) * 16;
+    auto wait_ms = wait_ns / 1000000;
+
+    WaitOnAddress(w, &value, 4, static_cast<DWORD>(wait_ms));
   }
 }
 
 void SpinLockWake(std::atomic<int> *w, bool all) {
+  if (all) {
+    WakeByAddressAll((void*)w);
+  } else {
+    WakeByAddressSingle((void*)w);
+  }
 }
 
 } // namespace internal