Messages in this thread | | | Subject | Re: sched: memory corruption on completing completions | From | Davidlohr Bueso <> | Date | Thu, 05 Feb 2015 12:59:46 -0800 |
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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
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