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Date: Sun, 6 Apr 2008 23:20:08 -0700 (PDT) From: Christoph Lameter <clameter@....com> To: Andrea Arcangeli <andrea@...ranet.com> cc: Robin Holt <holt@....com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, kvm-devel@...ts.sourceforge.net, Peter Zijlstra <a.p.zijlstra@...llo.nl>, general@...ts.openfabrics.org, steiner@....com, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [patch 02/10] emm: notifier logic On Mon, 7 Apr 2008, Andrea Arcangeli wrote: > > > My mm_lock solution makes all rcu serialization an unnecessary > > > overhead so you should remove it like I already did in #v11. If it > > > wasn't the case, then mm_lock wouldn't be a definitive fix for the > > > race. > > > > There still could be junk in the cache of one cpu. If you just read the > > new pointer but use the earlier content pointed to then you have a > > problem. > > There can't be junk, spinlocks provides semantics of proper memory > barriers, just like rcu, so it's entirely superflous. > > There could be junk only if any of the mmu_notifier_* methods would be > invoked _outside_ the i_mmap_lock and _outside_ the anon_vma and > outside the mmap_sem, that is never the case of course. So we use other locks to perform serialization on the list chains? Basically the list chains are protected by either mmap_sem or an rmap lock? We need to document that. In that case we could also add an unregister function. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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