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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /browser/app/winlauncher/freestanding/SafeThreadLocal.h
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'browser/app/winlauncher/freestanding/SafeThreadLocal.h')
-rw-r--r--browser/app/winlauncher/freestanding/SafeThreadLocal.h96
1 files changed, 96 insertions, 0 deletions
diff --git a/browser/app/winlauncher/freestanding/SafeThreadLocal.h b/browser/app/winlauncher/freestanding/SafeThreadLocal.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_freestanding_SafeThreadLocal_h
+#define mozilla_freestanding_SafeThreadLocal_h
+
+#include <type_traits>
+
+#include "mozilla/NativeNt.h"
+#include "mozilla/ThreadLocal.h"
+
+namespace mozilla {
+namespace freestanding {
+
+// We cannot fall back to the Tls* APIs because kernel32 might not have been
+// loaded yet.
+#if defined(__MINGW32__) && !defined(HAVE_THREAD_TLS_KEYWORD)
+# error "This code requires the compiler to have native TLS support"
+#endif // defined(__MINGW32__) && !defined(HAVE_THREAD_TLS_KEYWORD)
+
+/**
+ * This class holds data as a thread-local variable, or as a global variable
+ * if the thread local storage is not initialized yet. It should be safe
+ * because in that early stage we assume there is no more than a single thread.
+ */
+template <typename T>
+class SafeThreadLocal final {
+ static MOZ_THREAD_LOCAL(T) sThreadLocal;
+ static T sGlobal;
+ static bool sIsTlsUsed;
+
+ // In normal cases, TLS is always available and the class uses sThreadLocal
+ // without changing sMainThreadId. So sMainThreadId is likely to be 0.
+ //
+ // If TLS is not available, we use sGlobal instead and update sMainThreadId
+ // so that that thread keeps using sGlobal even after TLS is initialized
+ // later.
+ static DWORD sMainThreadId;
+
+ // Need non-inline accessors to prevent the compiler from generating code
+ // accessing sThreadLocal before checking a condition.
+ MOZ_NEVER_INLINE static void SetGlobalValue(T aValue) { sGlobal = aValue; }
+ MOZ_NEVER_INLINE static T GetGlobalValue() { return sGlobal; }
+
+ public:
+ static void set(T aValue) {
+ static_assert(std::is_pointer_v<T>,
+ "SafeThreadLocal must be used with a pointer");
+
+ if (sMainThreadId == mozilla::nt::RtlGetCurrentThreadId()) {
+ SetGlobalValue(aValue);
+ } else if (sIsTlsUsed) {
+ MOZ_ASSERT(mozilla::nt::RtlGetThreadLocalStoragePointer(),
+ "Once TLS is used, TLS should be available till the end.");
+ sThreadLocal.set(aValue);
+ } else if (mozilla::nt::RtlGetThreadLocalStoragePointer()) {
+ sIsTlsUsed = true;
+ sThreadLocal.set(aValue);
+ } else {
+ MOZ_ASSERT(sMainThreadId == 0,
+ "A second thread cannot be created before TLS is available.");
+ sMainThreadId = mozilla::nt::RtlGetCurrentThreadId();
+ SetGlobalValue(aValue);
+ }
+ }
+
+ static T get() {
+ if (sMainThreadId == mozilla::nt::RtlGetCurrentThreadId()) {
+ return GetGlobalValue();
+ } else if (sIsTlsUsed) {
+ return sThreadLocal.get();
+ }
+ return GetGlobalValue();
+ }
+};
+
+template <typename T>
+MOZ_THREAD_LOCAL(T)
+SafeThreadLocal<T>::sThreadLocal;
+
+template <typename T>
+T SafeThreadLocal<T>::sGlobal = nullptr;
+
+template <typename T>
+bool SafeThreadLocal<T>::sIsTlsUsed = false;
+
+template <typename T>
+DWORD SafeThreadLocal<T>::sMainThreadId = 0;
+
+} // namespace freestanding
+} // namespace mozilla
+
+#endif // mozilla_freestanding_SafeThreadLocal_h