linux-kernel - Re: [PATCH 3/7] regmap: Add a mutex to guard the sync operation

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Message-ID: <20110928142406.GA12438@opensource.wolfsonmicro.com>
Date:	Wed, 28 Sep 2011 15:24:06 +0100
From:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH 3/7] regmap: Add a mutex to guard the sync operation

On Wed, Sep 28, 2011 at 01:52:50PM +0100, Mark Brown wrote:
> On Wed, Sep 28, 2011 at 11:43:43AM +0100, Dimitris Papastamos wrote:
> 
> > +	mutex_lock(&map->sync_lock);
> >  	dev_dbg(map->dev, "Syncing %s cache\n",
> >  		map->cache_ops->name);
> >  	name = map->cache_ops->name;
> > @@ -254,6 +257,7 @@ int regcache_sync(struct regmap *map)
> >  	}
> >  out:
> >  	trace_regcache_sync(map->dev, name, "stop");
> > +	mutex_unlock(&map->sync_lock);
> 
> Shouldn't we either be taking the regmap lock when doing the sync or
> otherwise guarding against something other than a cache sync?

Em the main issue is that the sync() implementation will use
regmap_write() which will grab map->lock.  To avoid this we could have
gone and used directly the lockless _regmap_write() but that's
static.  To be honest, it feels cleaner to have only 1 lock to guard
the map so maybe we should get rid of map->sync_lock.
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