4 ms·

What is the source of the complexity inside condition variables? Reading the glibc sources, the main problem seems to be ensuring that signals are delivered pro

What is the source of the complexity inside condition variables? Reading the glibc sources, the main problem seems to be ensuring that signals are delivered properly?

zvrba 6y ago
Yes, atomic unlock + wait is the complex bit. Prior to Vista, Windows did not have a CV primitive. Existing emulations used multiple kernel objects and their correctness was difficult to verify. Performance also suffered.
- gpderetta 6y ago
  I think Vista implemented keyed synchronization objects (i.e. a flavour of futexes) which have similar edge triggered semantics as CVs.
atq2119 6y ago
It's possible to implement very simple condition variables. The tricky part is preventing correct but inefficient behaviours like stampeding herds.
- gpderetta 6y ago
  When implementing posix semantics there are a lot of nasty corner cases, especially with dealing with fairnes, graceful destruction, correct handling of wait generations and probably more that I'm missing. I would never attempt to implement a full condvar.