On Saturday, November 24, 2012 10:01:39 am Attilio Rao wrote: > On Sat, Nov 24, 2012 at 3:08 AM, Ryan Stone <ryst...@gmail.com> wrote: > > Today I saw a spurious witness warning for "acquiring duplicate lock of > > same type". The root cause is that when running mtx_destroy on a spinlock > > that is held by the current thread, mtx_destroy calls spinlock_exit() > > before calling WITNESS_UNLOCK, which opens up a window in which the CPU can > > be interrupted and attempt to acquire another spinlock of the same type as > > the one being destroyed. This patch should fix it: > > I seriously wonder why right now we don't assume the lock is unheld. > There are likely historically reasons for that, but I would like to > know which one are those and eventually fix them out. > FWIK, all the other locking primitives assume the lock is already > unheld when destroying and I think it would be good to have that for > mutexes as well.
That is simply behavior we inherited from BSD/OS. I didn't find it all that useful so all of the other locking primitives I've added since then have not had this behavior. -- John Baldwin _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
