fork of 9front i guess
4fc4b0dda7
the initial issue was that wunlock() would wakeup readers while holding the spinlock causing deadlock in libthread programs where rendezvous() would do a thread switch within the same process which then can acquire the RWLock again. the first fix tried to prevent holding the spinlock, waking up one reader at a time with releasing an re-acquiering the spinlock. this violates the invariant that readers can only wakup writers in runlock() when multiple readers where queued at the time of wunlock(). at the first wakeup, q->head != nil so runlock() would find a reader queued on runlock() when it expected a writer. this (hopefully last) fix unlinks *all* the reader QLp's atomically and in order while holding the spinlock and then traverses the dequeued chain of QLp structures again to call rendezvous() so the invariant described above holds. |
||
|---|---|---|
| 386 | ||
| 68000 | ||
| 68020 | ||
| acme | ||
| adm/timezone | ||
| amd64 | ||
| arm | ||
| lib | ||
| mips | ||
| power | ||
| power64 | ||
| rc | ||
| sparc | ||
| sparc64 | ||
| spim | ||
| sys | ||
| .hgignore | ||