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Message-ID: <87d203v56b.fsf@rustcorp.com.au>
Date: Wed, 08 Jul 2015 10:25:40 +0930
From: Rusty Russell <rusty@...tcorp.com.au>
To: Peter Zijlstra <peterz@...radead.org>,
Arthur Marsh <arthur.marsh@...ernode.on.net>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
linux-kernel@...r.kernel.org, rostedt <rostedt@...dmis.org>,
Oleg Nesterov <oleg@...hat.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: lock-up with module: Optimize __module_address() using a latched RB-tree
Peter Zijlstra <peterz@...radead.org> writes:
> On Tue, Jul 07, 2015 at 11:56:20PM +0200, Peter Zijlstra wrote:
>> On Wed, Jul 08, 2015 at 05:45:45AM +0930, Arthur Marsh wrote:
>> > I'm not aware of any modules being loaded with --force .
>> >
>> > I've applied the patch, thanks!
>> >
>> > The resultant kernel locked up as follows:
>> >
>> > http://www.users.on.net/~arthur.marsh/20150708469.jpg
>>
>> This has "Not tainted" which would indeed rule out forced loading. So
>> much for that idea :/
>>
>> > http://www.users.on.net/~arthur.marsh/20150708470.jpg
>>
>> And that one has a bunch of NMI prints, curious those. But given Mathieu
>> made them return NULL, that completely rules out the most interesting
>> races.
>
> Could you try the below? It appears there was a spot freeing modules
> that forgot to take them out of the tree.
Ouch! Good catch.
I'm testing that here.... Yep, "modprobe lp reset=7" (which fails to
parse) three times and then oops in __mod_tree_insert.
If you want to wrap that with a SOB and Reported-by/Tested-by if my
compatriot acks...
Thanks!
Rusty.
> ---
> kernel/module.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 3e0e19763d24..4d2b82e610e2 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3557,6 +3557,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
> mutex_lock(&module_mutex);
> /* Unlink carefully: kallsyms could be walking list. */
> list_del_rcu(&mod->list);
> + mod_tree_remove(mod);
> wake_up_all(&module_wq);
> /* Wait for RCU-sched synchronizing before releasing mod->list. */
> synchronize_sched();
--
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