Re: [PATCH] libfc: replace 'rp_mutex' with 'rp_lock'

[Hannes Reinecke <hare@suse.de>]

On 05/10/2016 08:33 PM, Bart Van Assche wrote:
> On 04/25/2016 01:01 AM, Hannes Reinecke wrote:
>> We cannot use an embedded mutex in a structure with reference
>> counting, as mutex unlock might be delayed, and the waiters
>> might then access an already freed memory area.
>> So convert it to a spinlock.
>>
>> For details cf https://lkml.org/lkml/2015/2/11/245
> 
> Hello Hannes,
> 
> Is what you describe a theoretical concern or have you observed any
> issues that could have been caused by the rport mutex? I'm asking
> this because my interpretation of the thread you refer to is
> different. My conclusion is that it is safe to embed a mutex in a
> structure that uses reference counting but that the mutex_unlock()
> call may trigger a spurious wakeup. I think that the conclusion of
> that thread was that glibc and kernel code should tolerate such
> spurious wakeups.
> 
We have several bugzillas referring to that specific code.
Most notably triggered when removing target ports with and open-fcoe
HBA.

And this patch seems to resolve it.
Read: with this patch the issue doesn't occur anymore.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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