Re: [PATCH v13 0/2] MR3504: ntdll: An implementation of SRWLOCK that closer matches Windows'.

[Zebediah Figura (＠zfigura)]

Zebediah Figura (@zfigura) commented about dlls/ntdll/sync.c:
> -
>    } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l);
> -
>        /* Someone else is also appending to the list, they have linked their
> -
>         * node to `prev`, but hasn't changed lock->Ptr yet. So we wait for
> -
>         * the lock to change and retry. */
> -
>        RtlWaitOnAddress(&lock->Ptr, &expected.Ptr, sizeof(expected.Ptr),
> -
>                         NULL);
> -
>        return FALSE;
> -
>    }
> - }
> -
>    if (!wait) return;
> -
>    RtlWaitOnAddress( u.s, &new.s, sizeof(struct srw_lock), NULL );
> - /* Once we reach here, `prev->next` can't be changed by anyone but us. So
> -
> * if we fail to change lock->Ptr, we have to reset it so others can append
> -
> * to the list. */
> - new = srwlock_from_waiter(&waiter, tag);

But this can't be possible, can it? Only the thread that successfully updated prev->next (i.e. this thread) can reach here. So that should just be assert(!prev), or am I missing something?