From: "Du, Changbin" <changbin.du@intel.com>
To: Felipe Balbi <balbi@kernel.org>
CC: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs_exit
Thread-Topic: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs_exit
Thread-Index: AQHRkXxyY3OKy5PsYkGv+nYrf2hue5+D6PoAgACmx7D//417AIAAiixQ//+FhwCAAW89kA==
Date: Tue, 12 Apr 2016 02:10:42 +0000
Message-ID: <0C18FE92A7765D4EB9EE5D38D86A563A05CFE62A@shsmsx102.ccr.corp.intel.com>
References: <1460108522-31664-1-git-send-email-changbin.du@intel.com>
 <87bn5gpo1v.fsf@intel.com>
 <0C18FE92A7765D4EB9EE5D38D86A563A05CFE203@shsmsx102.ccr.corp.intel.com>
 <87shyso0tp.fsf@intel.com>
 <0C18FE92A7765D4EB9EE5D38D86A563A05CFE28D@shsmsx102.ccr.corp.intel.com>
 <87mvp0ny81.fsf@intel.com>
In-Reply-To: <87mvp0ny81.fsf@intel.com>
Accept-Language: en-US
Content-Language: en-US
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 8BIT
MIME-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1451
Lines: 46

> Hi,
> 
> "Du, Changbin" <changbin.du@intel.com> writes:
> >>
> >> >> > +	dwc->regset = NULL;
> >> >>
> >> >> setting regset to NULL is unnecessary. We only call
> dwc3_debugfs_exit()
> >> >> when removing the driver.
> >> >>
> >> >> --
> >> >> Balbi
> >> > I'd like keep this line even it is unnecessary, because It is a good habit to
> >> > Avoid wild pointers. Just like the dwc->root = NULL.
> >>
> >> there won't be any wild pointers here, we'll free struct dwc3 *dwc itself.
> >>
> >> --
> >> Balbi
> > I agree the dwc will be freed in current code. But the 'free' logical is out
> > of the debugfs code. They should be treat as some logical independent.
> Per
> > this point, I still think set pointer to null is not bad. For example, if dwc3
> core
> > code invoke dwc3_debugfs_exit twice by mistake(just an example case,
> not
> > really), then no crash/impact for the second call.
> 
> the second call should crash because it's clearly wrong ;-) If dwc3 ever
> calls dwc3_debugfs_exit() twice, it really deserves to crash. It's
> something so wrong that we want the verbosity and urgency of a kernel
> oops to make sure we fix it ASAP.
> 
> If, however, we set it to null, it might be years before we notice
> anything's wrong.
> 
> --
> Balbi

Hmm, I agree from this point. I will combine this patch with other two patches
(due to their dependency). And I'd like remove the 'dwc->root=NULL' as well,
Is it ok for you?

Thx,
Du, Changbin