netdev - Re: [PATCH 25/33] sfc: Generate unique names for per-NIC workqueues

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Message-ID: <20081213140154.GK10372@solarflare.com>
Date:	Sat, 13 Dec 2008 14:01:56 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, linux-net-drivers@...arflare.com
Subject: Re: [PATCH 25/33] sfc: Generate unique names for per-NIC workqueues

David Miller wrote:
> From: Ben Hutchings <bhutchings@...arflare.com>
> Date: Sat, 13 Dec 2008 06:23:03 +0000
> 
> > David Miller wrote:
> > > create_singlethread_workqueue() is going to reference this
> > > name buffer on the stack for the life of the workqueue, but
> > > once this function returns that reference will no longer
> > > be valid.
> >  
> > No, it's copied into the "comm" field of task_struct.
> 
> Hmmm...
> 
> create_singlethread_workqueue(name...
> 	--> __create_workqueue(name...
> 	--> __create_workqueue_key(name...
> 
> which goes:
> 	wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
>  ...
> 	wq->name = name;
> 
> Which looks like a dynamic memory assumption to me.

If you look carefully you'll see that wq->name is never used after
initialisation of single-threaded workqueues.  But I'd agree it's not
nice to have that dangling pointer around, so I'll respin this.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
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