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AK: Add static Singleton::get function to allow destructible globals

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This enable using global raw pointers rather than Singleton objects,
which solves some problems because global Singleton object could
be deleted when destructors are run.
This commit is contained in:
Tom 2021-01-08 12:01:53 -07:00 committed by Andreas Kling
parent 8548ec357c
commit 1fc7d65aad
Notes: sideshowbarker 2024-07-18 23:58:56 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/1fc7d65aade
Pull-request: https://github.com/SerenityOS/serenity/pull/4854
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/alimpfard
1 changed files with 27 additions and 17 deletions
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44
AK/Singleton.h
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@ -56,36 +56,46 @@ class Singleton {
public:
Singleton() = default;
T* ptr() const
template<bool allow_create = true>
static T* get(T*& obj_var)
{
T* obj = AK::atomic_load(&m_obj, AK::memory_order_consume);
T* obj = AK::atomic_load(&obj_var, AK::memory_order_acquire);
if (FlatPtr(obj) <= 0x1) {
// If this is the first time, see if we get to initialize it
#ifdef KERNEL
Kernel::ScopedCritical critical;
#endif
if (obj == nullptr && AK::atomic_compare_exchange_strong(&m_obj, obj, (T*)0x1, AK::memory_order_acq_rel)) {
// We're the first one
obj = InitFunction();
AK::atomic_store(&m_obj, obj, AK::memory_order_release);
} else {
// Someone else was faster, wait until they're done
while (obj == (T*)0x1) {
#ifdef KERNEL
Kernel::Processor::wait_check();
#else
// TODO: yield
#endif
obj = AK::atomic_load(&m_obj, AK::memory_order_consume);
if constexpr (allow_create) {
if (obj == nullptr && AK::atomic_compare_exchange_strong(&obj_var, obj, (T*)0x1, AK::memory_order_acq_rel)) {
// We're the first one
obj = InitFunction();
AK::atomic_store(&obj_var, obj, AK::memory_order_release);
return obj;
}
}
// We should always return an instance
ASSERT(obj != nullptr);
// Someone else was faster, wait until they're done
while (obj == (T*)0x1) {
#ifdef KERNEL
Kernel::Processor::wait_check();
#else
// TODO: yield
#endif
obj = AK::atomic_load(&obj_var, AK::memory_order_acquire);
}
if constexpr (allow_create) {
// We should always return an instance if we allow creating one
ASSERT(obj != nullptr);
}
ASSERT(obj != (T*)0x1);
}
return obj;
}
T* ptr() const
{
return get(m_obj);
}
T* operator->() const
{
return ptr();