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Date:   Fri, 13 Nov 2020 13:30:35 +0100
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, 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>,
        tglx@linutronix.de
Subject: Re: [PATCH v4] kcov, usb: only collect coverage from
 __usb_hcd_giveback_urb in softirq
Message-ID: <20201113123035.tjllvijjzd54npsf@linutronix.de>
References: <f3a7a153f0719cb53ec385b16e912798bd3e4cf9.1602856358.git.andreyknvl@google.com>
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In-Reply-To: <f3a7a153f0719cb53ec385b16e912798bd3e4cf9.1602856358.git.andreyknvl@google.com>
Precedence: bulk

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?  

> +		kcov_remote_start_usb((u64)urb->dev->bus->busnum);
>  	urb->complete(urb);
> -	kcov_remote_stop();
> +	if (in_serving_softirq())
> +		kcov_remote_stop();
>  
>  	usb_anchor_resume_wakeups(anchor);
>  	atomic_dec(&urb->use_count);

Sebastian