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

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Message-ID: <0C18FE92A7765D4EB9EE5D38D86A563A05CFE62A@shsmsx102.ccr.corp.intel.com>
Date:	Tue, 12 Apr 2016 02:10:42 +0000
From:	"Du, Changbin" <changbin.du@...el.com>
To:	Felipe Balbi <balbi@...nel.org>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.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

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