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Subject: Re: [PATCH] Bluetooth: Collect kcov coverage from hci_rx_work
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20220517094532.2729049-1-poprdi@google.com>
Date:   Thu, 2 Jun 2022 17:29:07 +0200
Cc:     theflow@google.com, Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Message-Id: <16B0E861-298D-4038-A38E-E41C3046EE9C@holtmann.org>
References: <20220517094532.2729049-1-poprdi@google.com>
To:     Tamas Koczka <poprdi@google.com>
Precedence: bulk

Hi Tamas,

> Annotate hci_rx_work() with kcov_remote_start() and kcov_remote_stop()
> calls, so remote KCOV coverage is collected while processing the rx_q
> queue which is the main incoming Bluetooth packet queue.
> 
> Coverage is associated with the thread which created the packet skb.
> 
> Signed-off-by: Tamas Koczka <poprdi@google.com>
> ---
> net/bluetooth/hci_core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 45c2dd2e1590..703722031b8d 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -29,6 +29,7 @@
> #include <linux/rfkill.h>
> #include <linux/debugfs.h>
> #include <linux/crypto.h>
> +#include <linux/kcov.h>
> #include <linux/property.h>
> #include <linux/suspend.h>
> #include <linux/wait.h>
> @@ -3780,7 +3781,9 @@ static void hci_rx_work(struct work_struct *work)
> 
> 	BT_DBG("%s", hdev->name);
> 
> -	while ((skb = skb_dequeue(&hdev->rx_q))) {
> +	for (; (skb = skb_dequeue(&hdev->rx_q)); kcov_remote_stop()) {
> +		kcov_remote_start_common(skb_get_kcov_handle(skb));
> +
> 		/* Send copy to monitor */
> 		hci_send_to_monitor(hdev, skb);

patch looks good, but do you mind adding a comment above on why this is done. I asked, because next time around I look at this code I have forgotten all about it. Thanks.

Regards

Marcel