ReadGuard ReadWriteLock::TryRead()
{
u32 current_key = (mMutualExclusivityMask & READ_COUNT_MASK);
u32 insert_key = current_key + 1;
const bool success = (atomic_compare_and_swap(&mMutualExclusivityMask, current_key, insert_key) == current_key);
return success ? ReadGuard(this) : ReadGuard(nullptr);
}
ReadGuard ReadWriteLock::Read()
{
const u32 lock_key(EXCL_ENCODE(exclusive_write, 0));
// No need to encode since we know the insert counter exclusively owns the lower 28 bits of mMutualExclusivityMask.
// mask off the mutualexclusitivity to get the insert count. should aquire (or keep) insert exclusivity by inrementing insert count.
const ThreadID threadID = GetCurrentThreadId();
u32 current_key = (mMutualExclusivityMask & READ_COUNT_MASK);
u32 insert_key = current_key + 1;
while (atomic_compare_and_swap(&mMutualExclusivityMask, current_key, insert_key) != current_key)
{
if (threadID == mWriteEntryThread && mMutualExclusivityMask == lock_key)
{
atomic_increment((u32*)&mReentrancyCount);
break;
}
cond_wait();
current_key = (mMutualExclusivityMask & READ_COUNT_MASK);
insert_key = current_key + 1;
}
return ReadGuard(this);
}
inline ReadGuard read_guard() {
return ReadGuard(this);
}