linux-kernel - Re: [PATCH v2] kcov, usbip: collect coverage from vhci_rx

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Date:   Fri, 16 Oct 2020 16:18:14 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Shuah Khan <shuah@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Aleksandr Nogikh <nogikh@...gle.com>,
        Nazime Hande Harputluoglu <handeharput@...il.com>,
        Nazime Hande Harputluoglu <handeharputlu@...gle.com>
Subject: Re: [PATCH v2] kcov, usbip: collect coverage from vhci_rx_loop

On Tue, Oct 13, 2020 at 7:28 PM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> On 10/12/20 11:10 AM, Andrey Konovalov wrote:
> > From: Nazime Hande Harputluoglu <handeharputlu@...gle.com>
> >
> > Add kcov_remote_start()/kcov_remote_stop() annotations to the
> > vhci_rx_loop() function, which is responsible for parsing USB/IP packets
> > coming into USB/IP client.
> >
> > Since vhci_rx_loop() threads are spawned per vhci_hcd device instance, the
> > common kcov handle is used for kcov_remote_start()/stop() annotations
> > (see Documentation/dev-tools/kcov.rst for details). As the result kcov
> > can now be used to collect coverage from vhci_rx_loop() threads.
> >
> > Signed-off-by: Nazime Hande Harputluoglu <handeharputlu@...gle.com>
> > ---
> >
> > Changes v1->v2:
> > - Fix spacing issues.
> > - Add ifdef CONFIG_KCOV around kcov_handle in usbip_device struct.
> >
>
> Does this compile without CONFIG_KCOV?
>
> > ---
> >   drivers/usb/usbip/usbip_common.h |  4 ++++
> >   drivers/usb/usbip/vhci_rx.c      |  3 +++
> >   drivers/usb/usbip/vhci_sysfs.c   | 12 +++++++-----
> >   3 files changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
> > index 8be857a4fa13..0906182011d6 100644
> > --- a/drivers/usb/usbip/usbip_common.h
> > +++ b/drivers/usb/usbip/usbip_common.h
> > @@ -277,6 +277,10 @@ struct usbip_device {
> >               void (*reset)(struct usbip_device *);
> >               void (*unusable)(struct usbip_device *);
> >       } eh_ops;
> > +
> > +#ifdef CONFIG_KCOV
> > +     u64 kcov_handle;
> > +#endif

Hi Shuah,

We could have this field always defined, which allows us to not check
CONFIG_KCOV in the places where it's used (this is what we do for
vhost; the kcov functions will be optimized away). Or we could keep
the ifdef CONFIG_KCOV check here, and then add the same checks to
other places.

What would be your preference here?

Thanks!