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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
/*
* GC-internal classes for acquiring and releasing the GC lock.
*/
#ifndef gc_GCLock_h
#define gc_GCLock_h
#include "vm/Runtime.h"
namespace js {
class AutoUnlockGC;
/*
* RAII class that takes the GC lock while it is live.
*
* Usually functions will pass const references of this class. However
* non-const references can be used to either temporarily release the lock by
* use of AutoUnlockGC or to start background allocation when the lock is
* released.
*/
class MOZ_RAII AutoLockGC {
public:
explicit AutoLockGC(gc::GCRuntime* gc) : gc(gc) { lock(); }
explicit AutoLockGC(JSRuntime* rt) : AutoLockGC(&rt->gc) {}
~AutoLockGC() { lockGuard_.reset(); }
js::LockGuard<js::Mutex>& guard() { return lockGuard_.ref(); }
protected:
void lock() {
MOZ_ASSERT(lockGuard_.isNothing());
lockGuard_.emplace(gc->lock);
}
void unlock() {
MOZ_ASSERT(lockGuard_.isSome());
lockGuard_.reset();
}
gc::GCRuntime* const gc;
private:
mozilla::Maybe<js::LockGuard<js::Mutex>> lockGuard_;
AutoLockGC(const AutoLockGC&) = delete;
AutoLockGC& operator=(const AutoLockGC&) = delete;
friend class AutoUnlockGC; // For lock/unlock.
};
/*
* Same as AutoLockGC except it can optionally start a background chunk
* allocation task when the lock is released.
*/
class MOZ_RAII AutoLockGCBgAlloc : public AutoLockGC {
public:
explicit AutoLockGCBgAlloc(gc::GCRuntime* gc) : AutoLockGC(gc) {}
explicit AutoLockGCBgAlloc(JSRuntime* rt) : AutoLockGCBgAlloc(&rt->gc) {}
~AutoLockGCBgAlloc() {
unlock();
/*
* We have to do this after releasing the lock because it may acquire
* the helper lock which could cause lock inversion if we still held
* the GC lock.
*/
if (startBgAlloc) {
gc->startBackgroundAllocTaskIfIdle();
}
}
/*
* This can be used to start a background allocation task (if one isn't
* already running) that allocates chunks and makes them available in the
* free chunks list. This happens after the lock is released in order to
* avoid lock inversion.
*/
void tryToStartBackgroundAllocation() { startBgAlloc = true; }
private:
// true if we should start a background chunk allocation task after the
// lock is released.
bool startBgAlloc = false;
};
class MOZ_RAII AutoUnlockGC {
public:
explicit AutoUnlockGC(AutoLockGC& lock) : lock(lock) { lock.unlock(); }
~AutoUnlockGC() { lock.lock(); }
private:
AutoLockGC& lock;
AutoUnlockGC(const AutoUnlockGC&) = delete;
AutoUnlockGC& operator=(const AutoUnlockGC&) = delete;
};
} // namespace js
#endif /* gc_GCLock_h */