linux-kernel - Re: [PATCH v4] drivers/net: process the result of hdlc_open() and add call of hdlc_close() in uhdlc

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Message-ID: <1005f190-8c03-bb5d-214c-c7fca9dd876b@csgroup.eu>
Date:   Mon, 4 Sep 2023 17:03:28 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Alexandra Diupina <adiupina@...ralinux.ru>,
        Zhao Qiang <qiang.zhao@....com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "David S. Miller" <davem@...emloft.net>,
        "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: Re: [PATCH v4] drivers/net: process the result of hdlc_open() and add
 call of hdlc_close() in uhdlc_close()



Le 04/09/2023 à 14:31, Alexandra Diupina a écrit :
> Process the result of hdlc_open() and call uhdlc_close()
> in case of an error. It is necessary to pass the error
> code up the control flow, similar to a possible
> error in request_irq().
> Also add a hdlc_close() call to the uhdlc_close()
> because the comment to hdlc_close() says it must be called
> by the hardware driver when the HDLC device is being closed
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: c19b6d246a35 ("drivers/net: support hdlc function for QE-UCC")
> Signed-off-by: Alexandra Diupina <adiupina@...ralinux.ru>
> ---
> v4: undo all the things done prior to hdlc_open() as
> Jakub Kicinski <kuba@...nel.org> suggested,
> add hdlc_close() call to the uhdlc_close() to match the function comment,
> add uhdlc_close() declaration to the top of the file not to put the
> uhdlc_close() function definition before uhdlc_open()
> v3: Fix the commits tree
> v2: Remove the 'rc' variable (stores the return value of the
> hdlc_open()) as Christophe Leroy <christophe.leroy@...roup.eu> suggested
>   drivers/net/wan/fsl_ucc_hdlc.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wan/fsl_ucc_hdlc.c b/drivers/net/wan/fsl_ucc_hdlc.c
> index 47c2ad7a3e42..fd999dabdd39 100644
> --- a/drivers/net/wan/fsl_ucc_hdlc.c
> +++ b/drivers/net/wan/fsl_ucc_hdlc.c
> @@ -34,6 +34,8 @@
>   #define TDM_PPPOHT_SLIC_MAXIN
>   #define RX_BD_ERRORS (R_CD_S | R_OV_S | R_CR_S | R_AB_S | R_NO_S | R_LG_S)
>   
> +static int uhdlc_close(struct net_device *dev);
> +
>   static struct ucc_tdm_info utdm_primary_info = {
>   	.uf_info = {
>   		.tsa = 0,
> @@ -731,7 +733,9 @@ static int uhdlc_open(struct net_device *dev)
>   		napi_enable(&priv->napi);
>   		netdev_reset_queue(dev);
>   		netif_start_queue(dev);
> -		hdlc_open(dev);
> +
> +		int rc = hdlc_open(dev);

Do not mix declarations and code. Please put all declaration at the top 
of the block.

> +		return rc == 0 ? 0 : (uhdlc_close(dev), rc);
>   	}

That's not easy to read.

I know that's more changes, but I'd prefer something like:

static int uhdlc_open(struct net_device *dev)
{
	u32 cecr_subblock;
	hdlc_device *hdlc = dev_to_hdlc(dev);
	struct ucc_hdlc_private *priv = hdlc->priv;
	struct ucc_tdm *utdm = priv->utdm;
	int rc;

	if (priv->hdlc_busy != 1)
		return 0;

	if (request_irq(priv->ut_info->uf_info.irq,
			ucc_hdlc_irq_handler, 0, "hdlc", priv))
		return -ENODEV;

	cecr_subblock = ucc_fast_get_qe_cr_subblock(
				priv->ut_info->uf_info.ucc_num);

	qe_issue_cmd(QE_INIT_TX_RX, cecr_subblock,
		     QE_CR_PROTOCOL_UNSPECIFIED, 0);

	ucc_fast_enable(priv->uccf, COMM_DIR_RX | COMM_DIR_TX);

	/* Enable the TDM port */
	if (priv->tsa)
		qe_setbits_8(&utdm->si_regs->siglmr1_h, 0x1 << utdm->tdm_port);

	priv->hdlc_busy = 1;
	netif_device_attach(priv->ndev);
	napi_enable(&priv->napi);
	netdev_reset_queue(dev);
	netif_start_queue(dev);

	rc = hdlc_open(dev);
	if (rc)
		uhdlc_close(dev);

	return rc;
}



>   
>   	return 0;
> @@ -824,6 +828,8 @@ static int uhdlc_close(struct net_device *dev)
>   	netdev_reset_queue(dev);
>   	priv->hdlc_busy = 0;
>   
> +	hdlc_close(dev);
> +
>   	return 0;
>   }
>   


And while you are looking at the correctness of this code, is it sure 
that uhdlc_open() cannot be called twice in parallele ?
If it can be called in parallèle I think the "if (priv->hdlc_busy != 1)" 
should be replaced by something using cmpxchg()