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Date: Thu, 26 May 2016 02:15:47 +0000 From: "Du, Changbin" <changbin.du@...el.com> To: Greg KH <gregkh@...uxfoundation.org>, Alan Stern <stern@...land.harvard.edu> CC: "mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>, "stefan.koch10@...il.com" <stefan.koch10@...il.com>, "hkallweit1@...il.com" <hkallweit1@...il.com>, "sergei.shtylyov@...entembedded.com" <sergei.shtylyov@...entembedded.com>, "jonas.hesselmann@...mail.de" <jonas.hesselmann@...mail.de>, "mingo@...nel.org" <mingo@...nel.org>, "paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "keescook@...omium.org" <keescook@...omium.org>, "Williams, Dan J" <dan.j.williams@...el.com>, "aryabinin@...tuozzo.com" <aryabinin@...tuozzo.com>, "tj@...nel.org" <tj@...nel.org>, "dave@...olabs.net" <dave@...olabs.net>, "nikolay@...ulusnetworks.com" <nikolay@...ulusnetworks.com>, "dvyukov@...gle.com" <dvyukov@...gle.com>, "adrien+dev@...ischi.me" <adrien+dev@...ischi.me>, "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, "linux-kernel@...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 > I agree with you two now after checking all urb code. I am sorry to disturb you. I did have an object lifetime issue, but it is of usb_request. I expect the cause is usb_request is freed but still pending in udc core. Then I cannot reproduce it, I even cannot know which function driver the usb_request came from. I originally want to use debugojects to debug that issue, then I though this can also help urb debugging. Obviously I am wrong. As you said reference counting of urbs is already present. :) I may add debugojects for device mode usb_request farther. Sometimes it helps. Thank you, Du, Changbin
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