linux-kernel - Re: [PATCH v9 16/16] staging: r8188eu: remove usb_vendor_req

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Date:   Thu, 23 Sep 2021 14:13:25 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Greg KH <greg@...ah.com>
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        David Laight <david.Laight@...lab.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Martin Kaiser <martin@...ser.cx>
Subject: Re: [PATCH v9 16/16] staging: r8188eu: remove usb_vendor_req_mutex

On 9/23/21 14:07, Greg KH wrote:
> On Thu, Sep 23, 2021 at 01:12:53PM +0300, Pavel Skripkin wrote:
>> On 9/23/21 11:47, Pavel Skripkin wrote:
>> > On 9/22/21 16:21, Pavel Skripkin wrote:
>> > > On 9/21/21 21:18, Fabio M. De Francesco wrote:
>> > > > From: Pavel Skripkin <paskripkin@...il.com>
>> > > > 
>> > > > This mutex was used to protect shared buffer for USB requests. Since
>> > > > buffer was removed in previous patch we can remove this mutex as well.
>> > > > 
>> > > > Furthermore, because it was used to serialize the calls to the Core USB
>> > > > API, we thoroughly tested the enabling of concurrent firing of USB requests
>> > > > without the mutex and found no problems of any kind in common use cases.
>> > > > 
>> > > > Co-developed-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
>> > > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
>> > > > Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
>> > > 
>> > > Hi, Greg!
>> > > 
>> > > If all is OK with previous 15 patches, please, do not take this one, it
>> > >    causes problems with connection... :)
>> > > 
>> > > I don't understand what went wrong after v8, but anyway, this one should
>> > > not be applied for now, since it's broken
>> > > 
>> > > 
>> > > Thank you
>> > > 
>> > > 
>> > 
>> > 
>> > Just to be clear: previous 15 patches _are_ tested and do not cause any
>> > misbehavior or bugs.
>> > 
>> > I guess, the stack buffer maybe the problem here, since it's the only
>> > change on this side since v8. I didn't have a chance to take a closer
>> > look, but I will do it on weekends, I hope :)
>> > 
>> 
>> Oh, I found the problem by just looking at the code with clear mind:
>> 
>> > -free_dvobj:
>> > -	if (status != _SUCCESS && pdvobjpriv) {
>> > +	if (pdvobjpriv) {
>> >  		usb_set_intfdata(usb_intf, NULL);
>> >  		kfree(pdvobjpriv);
>> >  		pdvobjpriv = NULL;
>> 
>> This if should be deleted completely, because we don't want to fail on every
>> probe :)
>> 
>> Sorry for noise... :(
>> 
>> Greg, can you take first 15 patches, if they look good and then I will send
>> fixed version of 16? AFAIU, you are ok with taking part of the series
> 
> Please fix up and resend the whole series as our tools work best by
> taking the whole thing.
> 
> That way I "know" you tested them all :)

It is true, but there was small error on testing side from me this time.

I am testing with qemu and I forgot to copy new driver to qemu's shared 
folder (it was busy day or I was already asleep, idk). It resulted to 
testing old version of the driver. Next day I've tested new changes on 
top of this series and found the problem :)

I am sorry for kind of lying, i've already fixed it locally, so it won't 
happen again



With regards,
Pavel Skripkin