On Wed, 2015-02-04 at 16:16 -0800, Linus Torvalds wrote: > And looking at the arch version, I think the paravirtualized code is crap. > > It does: > > prev = *lock; > add_smp(&lock->tickets.head, TICKET_LOCK_INC); > > /* add_smp() is a full mb() */ > > if (unlikely(lock->tickets.tail & TICKET_SLOWPATH_FLAG)) > __ticket_unlock_slowpath(lock, prev); > > > which is *exactly* the kind of things you cannot do with spinlocks, > because after you've done the "add_smp()" and released the spinlock > for the fast-path, you can't access the spinlock any more. Exactly > because a fast-path lock migth come in, and release the whole data > structure. > > As usual, the paravirt code is a horribly buggy heap of crud. Film at 11.
Per http://lwn.net/Articles/495597/ which clearly describes the intent of the slowpath unlocking. Cc'ing Raghavendra. Thanks, Davidlohr -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
