linux-kernel - Re: get_device in device_create

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Message-Id: <20060802144908.3645e08a.zaitcev@redhat.com>
Date:	Wed, 2 Aug 2006 14:49:08 -0700
From:	Pete Zaitcev <zaitcev@...hat.com>
To:	Dmitry Torokhov <dtor@...ightbb.com>
Cc:	greg@...ah.com, linux-kernel@...r.kernel.org, zaitcev@...hat.com
Subject: Re: get_device in device_create_file

On Tue, 1 Aug 2006 21:13:05 -0400, Dmitry Torokhov <dtor@...ightbb.com> wrote:

> > > 	if (get_device(dev)) {
> > > 		error = sysfs_create_file(&dev->kobj, &attr->attr);
> > > 		put_device(dev);
> > > 	}

> > Buf it not, and the caller has a reference, then the call to
> > get_device is redundant.

> Yes it is. There are few of redundant gets and puts sprinkled around
> in the driver core, but the last time I mentioned that Greg was not
> quite ready to get rid of them ;)

I see a small, but nonzero harm from keeping them, for two reasons.
One, I reviewed a patch for RHEL-4 today, where the submitter copied
this code without thinking. So, if we don't flush these, they will
proliferate. Hackers assume that if Greg wrote that, it must be the
right way. Two, these calls shrink the race window and may be
masking something.

-- Pete
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