linux-kernel - Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event

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Message-ID: <CAHdPZaPwUHHUyvgU1N=FAggF5Gg_p7cf-290Yd1+i+9eNyDY1g@mail.gmail.com>
Date:	Fri, 10 Aug 2012 10:00:55 +0530
From:	"devendra.aaru" <devendra.aaru@...il.com>
To:	Ben Chan <benchan@...omium.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init

On Wed, Jul 25, 2012 at 7:23 PM, Ben Chan <benchan@...omium.org> wrote:
> Hi Devendra,
>
> Thanks for cleaning up the driver.  If I understand the code
> correctly, the original author wanted to initialize wm_event once and
> reuse it for multiple devices, and thus reference counted it with
> ref_cnt.
>
> For instance, each time gdm_usb_probe() is called, it may call
> register_wimax_device() / gdm_wimax_event_init(). wm_event is
> initialized the first time when wm_event.ref_cnt == 0 (alternatively,
> the code could check !wm_event.sock). Subsequent calls to
> gdm_wimax_event_init() will simply increase the ref count. Similarly,
> gdm_usb_disconnect() calls unregister_wimax_device() /
> gdm_wimax_event_exit(), which decreases the ref count and disposes
> wm_event when ref_cnt becomes zero.
>
> The code change in commit 8df858ea76b76dde9a39d4edd9aaded983582cfe
> only prevents ref_cnt from increasing beyond one. So the code no
> longer work when there are multiple devices (i.e. wm_event could be
> disposed even when there is an active device).
>
> Thanks,
> Ben
>
>
Sorry Ben, I didn't saw the mail for a long time,

Thanks a lot for the long explanation, i will keep in mind of these
problems, and also i think your patch is ok.

Thanks,
Devendra.
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