linux-kernel - Re: [PATCH v4] kcov, usb: only collect coverage from __usb_hcd_giveback

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Date:   Fri, 13 Nov 2020 13:51:19 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB list <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.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>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4] kcov, usb: only collect coverage from
 __usb_hcd_giveback_urb in softirq

On Fri, Nov 13, 2020 at 1:30 PM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> On 2020-10-16 15:57:45 [+0200], Andrey Konovalov wrote:
> > --- a/drivers/usb/core/hcd.c
> > +++ b/drivers/usb/core/hcd.c
> > @@ -1646,9 +1646,16 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
> >
> >       /* pass ownership to the completion handler */
> >       urb->status = status;
> > -     kcov_remote_start_usb((u64)urb->dev->bus->busnum);
> > +     /*
> > +      * This function can be called in task context inside another remote
> > +      * coverage collection section, but KCOV doesn't support that kind of
> > +      * recursion yet. Only collect coverage in softirq context for now.
> > +      */
> > +     if (in_serving_softirq())
>
> Could this in_serving_softirq() usage be replaced, please?

Hi Sebastian,

Replaced with what and why?

Thanks!