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Date: Sat, 23 Oct 2010 17:24:25 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: Joe Buehler <aspam@....net> Cc: netdev@...r.kernel.org, David Daney <ddaney@...iumnetworks.com> Subject: Re: kernel panic in fib_rules_lookup [2.6.27.7 vendor-patched] Le samedi 23 octobre 2010 à 17:11 +0200, Eric Dumazet a écrit : > Le samedi 23 octobre 2010 à 05:44 +0200, Eric Dumazet a écrit : > > Le vendredi 22 octobre 2010 à 16:30 -0400, Joe Buehler a écrit : > > > Eric Dumazet wrote: > > > > > > > Could you provide a disassembly of function fib_rules_lookup ? > > > > > > Try looking in http://68.100.141.95:3000/linux-crash/. There should be > > > the source file I am using (not current release if you recall), the .o, > > > the disassembly, and a -S compile that makes deducing the line numbers a > > > little easier. > > > > > > > Hmm, I'll take a look sometime in the future, thanks > > Did that... Hmm... > > I am wondering if smp_rcu_assign_pointer() (or more precisely smp_wmb()) > is correctly implemented on octeon platform. > > Try to add in fib_nl_newrule() right after the kzalloc bloc : > > rule = kzalloc(ops->rule_size, GFP_KERNEL); > if (rule == NULL) { > err = -ENOMEM; > goto errout; > } > + rule->list.next = LIST_POISON1; > + rule->list.prev = LIST_POISON2; > > > So that we can actually see if the NULL dereference bug you hit becomes > a "LIST_POISON1" dereference bug... > > Reading commit 500c2e1fdbcc2b273bd is interesting... David Daney added a nudge_writes(), actually doing a "syncw" instruction, and this seems to be the smp_wmb() this platform should be using in the first place, not a pure compiler barrier (barrier()) So Joe, you might want to change the smp_wmb() call in rcu_assign_pointer() by the nudge_writes() call, and see what happens... -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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