linux-kernel - Re: [PATCH] usb: core: add debugobjects support for urb object

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Message-ID: <20160524144459.GD28161@kroah.com>
Date:	Tue, 24 May 2016 07:44:59 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	changbin.du@...el.com
Cc:	mathias.nyman@...ux.intel.com, stefan.koch10@...il.com,
	hkallweit1@...il.com, sergei.shtylyov@...entembedded.com,
	jonas.hesselmann@...mail.de, mingo@...nel.org,
	paulmck@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
	tglx@...utronix.de, keescook@...omium.org,
	dan.j.williams@...el.com, aryabinin@...tuozzo.com, tj@...nel.org,
	dave@...olabs.net, nikolay@...ulusnetworks.com, dvyukov@...gle.com,
	adrien+dev@...ischi.me, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: core: add debugobjects support for urb object

On Tue, May 24, 2016 at 03:53:53PM +0800, changbin.du@...el.com wrote:
> From: "Du, Changbin" <changbin.du@...el.com>
> 
> Add debugobject support to track the life time of struct urb.
> This feature help us detect violation of urb operations by
> generating a warning message from debugobject core. And we fix
> the possible issues at runtime to avoid oops if we can.
> 
> I have done some tests with some class drivers, no violation
> found in them which is good. Expect this feature can be used
> for debugging future problems.
> 
> Signed-off-by: Du, Changbin <changbin.du@...el.com>

I agree with Alan, what use is this code?  Existing drivers all work
properly because the reference counting of urbs is already present, why
add duplicate counters?  That actually leads to bugs.  I don't see the
need for this code, please explain it better if you wish for it to be
accepted.  What has it found/fixed that we have not found yet?  What
does it allow you to do that you can't do today with the existing code?

thanks,

greg k-h