linux-kernel - RE: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs

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Message-ID: <87mvp0ny81.fsf@intel.com>
Date:	Mon, 11 Apr 2016 15:09:34 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	"Du\, Changbin" <changbin.du@...el.com>
Cc:	"gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs_exit


Hi,

"Du, Changbin" <changbin.du@...el.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

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