Re: [PATCH v4] kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq

From: Andrey Konovalov <andreyknvl@google.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	USB list <linux-usb@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Shuah Khan <shuah@kernel.org>,
	Alexander Potapenko <glider@google.com>,
	Marco Elver <elver@google.com>,
	Aleksandr Nogikh <nogikh@google.com>,
	Nazime Hande Harputluoglu <handeharput@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v4] kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq
Date: Fri, 13 Nov 2020 13:51:19 +0100	[thread overview]
Message-ID: <CAAeHK+zd0ucaj8EJ8ro+0ekubrxp5GiBMaBULHJB05dDrzpQGw@mail.gmail.com> (raw)
In-Reply-To: <20201113123035.tjllvijjzd54npsf@linutronix.de>

On Fri, Nov 13, 2020 at 1:30 PM Sebastian Andrzej Siewior
<bigeasy@linutronix.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!