linux-kernel - Re: [PATCH] selftests: add sleep between detach and usbip list -l

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Message-ID: <20190506151540.GA12755@kroah.com>
Date:   Mon, 6 May 2019 17:15:40 +0200
From:   Greg KH <greg@...ah.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     valentina.manea.m@...il.com, shuah@...nel.org,
        linux-usb@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: add sleep between detach and usbip list -l

On Mon, May 06, 2019 at 08:47:15AM -0600, Shuah Khan wrote:
> On 5/5/19 3:13 AM, Greg KH wrote:
> > On Thu, May 02, 2019 at 01:47:40PM -0600, Shuah Khan wrote:
> > > Add a sleep between detach and check for exportable devices to avoid
> > > the following segfault from libc-2.27.so
> > > 
> > > [ 6268.136108] usbip[5565]: segfault at 0 ip 00007f2a947bddfd sp 00007ffd1a8705e8 error 4 in libc-2.27.so[7f2a94703000+1e7000]
> > > 
> > > Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> > > ---
> > >   tools/testing/selftests/drivers/usb/usbip/usbip_test.sh | 4 ++++
> > >   1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/tools/testing/selftests/drivers/usb/usbip/usbip_test.sh b/tools/testing/selftests/drivers/usb/usbip/usbip_test.sh
> > > index 128f0ab24307..beacf24a8df7 100755
> > > --- a/tools/testing/selftests/drivers/usb/usbip/usbip_test.sh
> > > +++ b/tools/testing/selftests/drivers/usb/usbip/usbip_test.sh
> > > @@ -171,10 +171,14 @@ echo "Detach invalid port tests - expect invalid port error message";
> > >   src/usbip detach -p 100;
> > >   echo "=============================================================="
> > > +# let detach complete. Avoid segfaults from libc-2.27.so
> > > +sleep 3;
> > 
> > That feels very "arbitrary", why do we "know" it will take at most 3
> > seconds?  I guess there's not much else we can do here except maybe
> > somehow watch sysfs until the device is really gone?
> > 
> 
> Yeah. Number 3 is somewhat arbitrary. It helps the host process the
> detach request from the client and update the sysfs. Detach returns
> as soon as client side is done, and the test is running the next
> command on the host side. If I were run these commands manually, it
> gives enough settling time. I am looking for a quick way to allow
> settling time in this automated test.

Ok, you might want to document that you know it's a random number :)

thanks,

greg k-h