On Sat, Nov 24, 2012 at 3:01 PM, Attilio Rao <atti...@freebsd.org> 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. > > Can you please show which lock triggers the panic you saw?
Ryan, however I'm sure this patch would introduce a major switch in our KPI/POLA and eventually it would be a bigger work. Your patch is certainly right and I think you should commit it for the time being. For the long-term, maybe you would like to work on such a patch, rather. Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ 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"
