LightweightSemaphore weak-try? #12

Activity

1. Caldfir

   changed the title [-]weak-try?[/-] [+]LightweightSemaphore weak-try?[/+] on Jul 5, 2021
2. Caldfir commented on Jul 5, 2021

   

   Caldfir

   on Jul 5, 2021

   Last edited by Caldfir

   Author

   More actions

   To clarify, the issue is that it seems to be possible for tryWait to return false while the semaphore is positive because CAS could fail from a signal() in another thread. The only resolution I can think of would be to loop:

   int oldCount;
   while (1)
   {
     oldCount = m_count.load(std::memory_order_relaxed);
     if (oldCount <= 0) return false;
     if (m_count.compare_exchange_weak(oldCount, oldCount - 1, std::memory_order_acquire)) return true;
   }

   But while(1) in a method called try... sounds obscene, even if in even the worst case this would only actually loop very infrequently.