Hacker News new | ask | show | jobs
by bingo3131 834 days ago
Misleading title?

This is a Windows API bug with the slim reader/writer (SRW) locks. It's just that the bug was discovered via std::shared_mutex as that is implemented using SRW locks.

SRW locks: https://learn.microsoft.com/en-us/windows/win32/sync/slim-re...

Confirmation from a Microsoft employee that the bug has been raised internally with the Windows API team: https://old.reddit.com/r/cpp/comments/1b55686/maybe_possible...
2 comments
dang 834 days ago
Ok, I've changed the title to say that. Thanks!
link
tialaramex 834 days ago
Yes, for example if you make a Rust std::sync:RWLock on Windows, it will literally be SRWLock because Microsoft advertises this API as having exactly the behaviour Rust wants so why would you build something worse instead ?

Rust's Mutex on Windows is also an SRWLock but it can't hit this bug because it deliberately only uses the exclusive locking.

link
iknowstuff 834 days ago
So it doesn't use a shared lock when .read() is used?
link
zozbot234 834 days ago
Rust has both Mutex and RWLock. The Mutex only uses exclusive locks, there's no distinction between "read" and "write".
link
iknowstuff 834 days ago
Oh sorry my morning brain thought the comment was all about RWLock
link