linux-kernel - Re: [2.4 patch] Port of adutux driver from 2.6 kernel to 2.4.

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Message-Id: <20071016105223.a0a8fe8c.zaitcev@redhat.com>
Date:	Tue, 16 Oct 2007 10:52:23 -0700
From:	Pete Zaitcev <zaitcev@...hat.com>
To:	vitalivanov@...il.com
Cc:	Willy Tarreau <w@....eu>, gregkh@...e.de,
	linux-usb-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, zaitcev@...hat.com
Subject: Re: [2.4 patch] Port of adutux driver from 2.6 kernel to 2.4.

On Tue, 16 Oct 2007 16:54:49 +0300, Vitaliy Ivanov <vitalivanov@...il.com> wrote:

> Again, comments are welcomed.

It looks like you misunderstood why a static lock protects open counts.
This is done so you do not need to worry about in-structure lock which
can be freed together with the structure. Look at this:

> +static int adu_release_internal(struct adu_device *dev)
> +{
> +	/* lock this device */
> +	down(&dev->sem);
> +	/* decrement our usage count for the device */
> +	--dev->open_count;
> +	if (dev->open_count <= 0) {
> +		adu_abort_transfers(dev);
> +		dev->open_count = 0;
> +	}
> +	/* unlock this device */
> +	up(&dev->sem);

The dev->sem is entirely unnecessary here. Every time you use
open_count, it's protected by minor_table_mutex. The name is a litte
unfortunate, feel free to rename it.

This is probably a problem in 2.6 as well. I don't know why people keep
writing these things. Someone at Ontrak needs to look into it.

-- Pete
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