From: Mike Mason <mmlnx@us•ibm.com>
To: michael@ellerman•id.au
Cc: linuxppc-dev@ozlabs•org, linasvepstas@gmail•com,
Paul Mackerras <paulus@samba•org>
Subject: Re: [PATCH] Hold reference to device_node during EEH event handling
Date: Thu, 16 Jul 2009 09:33:57 -0700 [thread overview]
Message-ID: <4A5F5675.6040104@us.ibm.com> (raw)
In-Reply-To: <1247708506.9851.8.camel@concordia>
Michael Ellerman wrote:
> On Wed, 2009-07-15 at 14:43 -0700, Mike Mason wrote:
>> This patch increments the device_node reference counter when an EEH
>> error occurs and decrements the counter when the event has been
>> handled. This is to prevent the device_node from being released until
>> eeh_event_handler() has had a chance to deal with the event. We've
>> seen cases where the device_node is released too soon when an EEH
>> event occurs during a dlpar remove, causing the event handler to
>> attempt to access bad memory locations.
>>
>> Please review and let me know of any concerns.
>
> Taking a reference sounds sane, but ...
>
>> Signed-off-by: Mike Mason <mmlnx@us•ibm.com>
>>
>> --- a/arch/powerpc/platforms/pseries/eeh_event.c 2008-10-09 15:13:53.000000000 -0700
>> +++ b/arch/powerpc/platforms/pseries/eeh_event.c 2009-07-14 14:14:00.000000000 -0700
>> @@ -75,6 +75,14 @@ static int eeh_event_handler(void * dumm
>> if (event == NULL)
>> return 0;
>>
>> + /* EEH holds a reference to the device_node, so if it
>> + * equals 1 it's no longer valid and the event should
>> + * be ignored */
>> + if (atomic_read(&event->dn->kref.refcount) == 1) {
>> + of_node_put(event->dn);
>> + return 0;
>> + }
>
> That's really gross :)
Agreed. I'll look for another way to determine if device is gone and the event should be ignored. Suggestions are welcome :-)
>
> And what happens if the refcount goes to 1 just after the check? ie.
> here.
>
>> /* Serialize processing of EEH events */
>> mutex_lock(&eeh_event_mutex);
>> eeh_mark_slot(event->dn, EEH_MODE_RECOVERING);
>
>
> cheers
>
next prev parent reply other threads:[~2009-07-16 16:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-15 21:43 [PATCH] Hold reference to device_node during EEH event handling Mike Mason
2009-07-16 1:41 ` Michael Ellerman
2009-07-16 16:33 ` Mike Mason [this message]
2009-07-17 0:36 ` Michael Ellerman
2009-07-22 23:41 ` Mike Mason
2009-07-23 1:21 ` Michael Ellerman
2009-07-23 14:16 ` Linas Vepstas
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