linux-kernel - Re: [PATCH] mm/dmapool.c: Do not create/destroy sysfs file while holding pools

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Date:	Tue, 1 Mar 2011 23:23:20 -0600
From:	Shaun Ruffell <sruffell@...ffell.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Russ Meyerriecks <rmeyerriecks@...ium.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Greg KH <greg@...ah.com>
Subject: Re: [PATCH] mm/dmapool.c: Do not create/destroy sysfs file while
	holding pools_lock

On Tue, Mar 01, 2011 at 08:35:53PM -0800, Eric W. Biederman wrote:
> Andrew Morton <akpm@...ux-foundation.org> writes:
> > One way of fixing this would be to create another singleton lock:
> >
> >
> > 	{
> > 		static DEFINE_MUTEX(pools_sysfs_lock);
> > 		static bool pools_sysfs_done;
> >
> > 		mutex_lock(&pools_sysfs_lock);
> > 		if (pools_sysfs_done == false) {
> > 			create_sysfs_stuff();
> > 			pools_sysfs_done = true;
> > 		}
> > 		mutex_unlock(&pools_sysfs_lock);
> > 	}
> >
> > That's not terribly pretty.
> 
> Or possibly use module_init style magic.  Where use module
> initialization and remove to trigger creation and deletion of the sysfs.
> 

I'm not following how module initialization can help here. Are you suggesting
that all devices get a 'pools' attribute regardless of whether any dma pools
are actually created?

Shaun
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