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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
#ifndef mozilla_glue_MozglueUtils_h
#define mozilla_glue_MozglueUtils_h
#include <windows.h>
#include "mozilla/Atomics.h"
#include "mozilla/Attributes.h"
namespace mozilla {
namespace glue {
#ifdef DEBUG
class MOZ_STATIC_CLASS Win32SRWLock final {
public:
// Microsoft guarantees that '0' is never a valid thread id
static const DWORD kInvalidThreadId = 0;
constexpr Win32SRWLock()
: mExclusiveThreadId(kInvalidThreadId), mLock(SRWLOCK_INIT) {}
~Win32SRWLock() { MOZ_ASSERT(mExclusiveThreadId == kInvalidThreadId); }
void LockShared() {
MOZ_ASSERT(
mExclusiveThreadId != GetCurrentThreadId(),
"Deadlock detected - A thread attempted to acquire a shared lock on "
"a SRWLOCK when it already owns the exclusive lock on it.");
::AcquireSRWLockShared(&mLock);
}
void UnlockShared() { ::ReleaseSRWLockShared(&mLock); }
void LockExclusive() {
MOZ_ASSERT(
mExclusiveThreadId != GetCurrentThreadId(),
"Deadlock detected - A thread attempted to acquire an exclusive lock "
"on a SRWLOCK when it already owns the exclusive lock on it.");
::AcquireSRWLockExclusive(&mLock);
mExclusiveThreadId = GetCurrentThreadId();
}
void UnlockExclusive() {
MOZ_ASSERT(mExclusiveThreadId == GetCurrentThreadId());
mExclusiveThreadId = kInvalidThreadId;
::ReleaseSRWLockExclusive(&mLock);
}
Win32SRWLock(const Win32SRWLock&) = delete;
Win32SRWLock(Win32SRWLock&&) = delete;
Win32SRWLock& operator=(const Win32SRWLock&) = delete;
Win32SRWLock& operator=(Win32SRWLock&&) = delete;
private:
// "Relaxed" memory ordering is fine. Threads will see other thread IDs
// appear here in some non-deterministic ordering (or not at all) and simply
// ignore them.
//
// But a thread will only read its own ID if it previously wrote it, and a
// single thread doesn't need a memory barrier to read its own write.
Atomic<DWORD, Relaxed> mExclusiveThreadId;
SRWLOCK mLock;
};
#else // DEBUG
class MOZ_STATIC_CLASS Win32SRWLock final {
public:
constexpr Win32SRWLock() : mLock(SRWLOCK_INIT) {}
void LockShared() { ::AcquireSRWLockShared(&mLock); }
void UnlockShared() { ::ReleaseSRWLockShared(&mLock); }
void LockExclusive() { ::AcquireSRWLockExclusive(&mLock); }
void UnlockExclusive() { ::ReleaseSRWLockExclusive(&mLock); }
~Win32SRWLock() = default;
Win32SRWLock(const Win32SRWLock&) = delete;
Win32SRWLock(Win32SRWLock&&) = delete;
Win32SRWLock& operator=(const Win32SRWLock&) = delete;
Win32SRWLock& operator=(Win32SRWLock&&) = delete;
private:
SRWLOCK mLock;
};
#endif
class MOZ_RAII AutoSharedLock final {
public:
explicit AutoSharedLock(Win32SRWLock& aLock) : mLock(aLock) {
mLock.LockShared();
}
~AutoSharedLock() { mLock.UnlockShared(); }
AutoSharedLock(const AutoSharedLock&) = delete;
AutoSharedLock(AutoSharedLock&&) = delete;
AutoSharedLock& operator=(const AutoSharedLock&) = delete;
AutoSharedLock& operator=(AutoSharedLock&&) = delete;
private:
Win32SRWLock& mLock;
};
class MOZ_RAII AutoExclusiveLock final {
public:
explicit AutoExclusiveLock(Win32SRWLock& aLock) : mLock(aLock) {
mLock.LockExclusive();
}
~AutoExclusiveLock() { mLock.UnlockExclusive(); }
AutoExclusiveLock(const AutoExclusiveLock&) = delete;
AutoExclusiveLock(AutoExclusiveLock&&) = delete;
AutoExclusiveLock& operator=(const AutoExclusiveLock&) = delete;
AutoExclusiveLock& operator=(AutoExclusiveLock&&) = delete;
private:
Win32SRWLock& mLock;
};
} // namespace glue
} // namespace mozilla
#endif // mozilla_glue_MozglueUtils_h