From 8d6b34f8630d6802e3570e8c6adcd2ad6fe4ddbe Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Sat, 28 Apr 2018 15:45:56 +0200
Subject: Use SRWlocks for js mutexes on Windows.

---
 js/src/threading/windows/ConditionVariable.cpp |  8 ++---
 js/src/threading/windows/MutexImpl.cpp         | 47 ++------------------------
 js/src/threading/windows/MutexPlatformData.h   |  2 +-
 3 files changed, 8 insertions(+), 49 deletions(-)

(limited to 'js/src')

diff --git a/js/src/threading/windows/ConditionVariable.cpp b/js/src/threading/windows/ConditionVariable.cpp
index 3c75a0f27..92e0249b7 100644
--- a/js/src/threading/windows/ConditionVariable.cpp
+++ b/js/src/threading/windows/ConditionVariable.cpp
@@ -54,8 +54,8 @@ js::ConditionVariable::notify_all()
 void
 js::ConditionVariable::wait(UniqueLock<Mutex>& lock)
 {
-  CRITICAL_SECTION* cs = &lock.lock.platformData()->criticalSection;
-  bool r = SleepConditionVariableCS(&platformData()->cv_, cs, INFINITE);
+  SRWLOCK* srwlock = &lock.lock.platformData()->lock;
+  bool r = SleepConditionVariableSRW(&platformData()->cv_, srwlock, INFINITE, 0);
   MOZ_RELEASE_ASSERT(r);
 }
 
@@ -70,7 +70,7 @@ js::CVStatus
 js::ConditionVariable::wait_for(UniqueLock<Mutex>& lock,
                                 const mozilla::TimeDuration& rel_time)
 {
-  CRITICAL_SECTION* cs = &lock.lock.platformData()->criticalSection;
+  SRWLOCK* srwlock = &lock.lock.platformData()->lock;
 
   // Note that DWORD is unsigned, so we have to be careful to clamp at 0.
   // If rel_time is Forever, then ToMilliseconds is +inf, which evaluates as
@@ -82,7 +82,7 @@ js::ConditionVariable::wait_for(UniqueLock<Mutex>& lock,
                  ? INFINITE
                  : static_cast<DWORD>(msecd);
 
-  BOOL r = SleepConditionVariableCS(&platformData()->cv_, cs, msec);
+  BOOL r = SleepConditionVariableSRW(&platformData()->cv_, srwlock, msec, 0);
   if (r)
     return CVStatus::NoTimeout;
   MOZ_RELEASE_ASSERT(GetLastError() == ERROR_TIMEOUT);
diff --git a/js/src/threading/windows/MutexImpl.cpp b/js/src/threading/windows/MutexImpl.cpp
index 385d1c8de..e838459b5 100644
--- a/js/src/threading/windows/MutexImpl.cpp
+++ b/js/src/threading/windows/MutexImpl.cpp
@@ -13,35 +13,6 @@
 #include "threading/Mutex.h"
 #include "threading/windows/MutexPlatformData.h"
 
-namespace {
-
-// We build with a toolkit that supports WinXP, so we have to probe
-// for modern features at runtime. This is necessary because Vista and
-// later automatically allocate and subsequently leak a debug info
-// object for each critical section that we allocate unless we tell it
-// not to. In order to tell it not to, we need the extra flags field
-// provided by the Ex version of InitializeCriticalSection.
-struct MutexNativeImports
-{
-  using InitializeCriticalSectionExT = BOOL (WINAPI*)(CRITICAL_SECTION*, DWORD, DWORD);
-  InitializeCriticalSectionExT InitializeCriticalSectionEx;
-
-  MutexNativeImports() {
-    HMODULE kernel32_dll = GetModuleHandle("kernel32.dll");
-    MOZ_RELEASE_ASSERT(kernel32_dll != NULL);
-    InitializeCriticalSectionEx = reinterpret_cast<InitializeCriticalSectionExT>(
-      GetProcAddress(kernel32_dll, "InitializeCriticalSectionEx"));
-  }
-
-  bool hasInitializeCriticalSectionEx() const {
-    return InitializeCriticalSectionEx;
-  }
-};
-
-static MutexNativeImports NativeImports;
-
-} // (anonymous namespace)
-
 js::detail::MutexImpl::MutexImpl()
 {
   AutoEnterOOMUnsafeRegion oom;
@@ -49,18 +20,7 @@ js::detail::MutexImpl::MutexImpl()
   if (!platformData_)
     oom.crash("js::Mutex::Mutex");
 
-  // This number was adopted from NSPR.
-  const static DWORD LockSpinCount = 1500;
-  BOOL r;
-  if (NativeImports.hasInitializeCriticalSectionEx()) {
-    r = NativeImports.InitializeCriticalSectionEx(&platformData()->criticalSection,
-                                                  LockSpinCount,
-                                                  CRITICAL_SECTION_NO_DEBUG_INFO);
-  } else {
-    r = InitializeCriticalSectionAndSpinCount(&platformData()->criticalSection,
-                                              LockSpinCount);
-  }
-  MOZ_RELEASE_ASSERT(r);
+  InitializeSRWLock(&platformData()->lock);
 }
 
 js::detail::MutexImpl::~MutexImpl()
@@ -68,18 +28,17 @@ js::detail::MutexImpl::~MutexImpl()
   if (!platformData_)
     return;
 
-  DeleteCriticalSection(&platformData()->criticalSection);
   js_delete(platformData());
 }
 
 void
 js::detail::MutexImpl::lock()
 {
-  EnterCriticalSection(&platformData()->criticalSection);
+  AcquireSRWLockExclusive(&platformData()->lock);
 }
 
 void
 js::detail::MutexImpl::unlock()
 {
-  LeaveCriticalSection(&platformData()->criticalSection);
+  ReleaseSRWLockExclusive(&platformData()->lock);
 }
diff --git a/js/src/threading/windows/MutexPlatformData.h b/js/src/threading/windows/MutexPlatformData.h
index fbe7fc80d..1d741c5d0 100644
--- a/js/src/threading/windows/MutexPlatformData.h
+++ b/js/src/threading/windows/MutexPlatformData.h
@@ -13,7 +13,7 @@
 
 struct js::detail::MutexImpl::PlatformData
 {
-  CRITICAL_SECTION criticalSection;
+  SRWLOCK lock;
 };
 
 #endif // platform_win_MutexPlatformData_h
-- 
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