netdev - Re: [PATCH net-next v11 4/5] net: rnpgbe: Add basic mbx

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Message-ID: <00A30C785FE598BA+20250910060821.GB1832711@nic-Precision-5820-Tower>
Date: Wed, 10 Sep 2025 14:08:21 +0800
From: Yibo Dong <dong100@...se.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "Anwar, Md Danish" <a0501179@...com>, andrew+netdev@...n.ch,
	davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
	horms@...nel.org, corbet@....net, gur.stavi@...wei.com,
	maddy@...ux.ibm.com, mpe@...erman.id.au, danishanwar@...com,
	lee@...ger.us, gongfan1@...wei.com, lorenzo@...nel.org,
	geert+renesas@...der.be, Parthiban.Veerasooran@...rochip.com,
	lukas.bulwahn@...hat.com, alexanderduyck@...com,
	richardcochran@...il.com, kees@...nel.org, gustavoars@...nel.org,
	rdunlap@...radead.org, vadim.fedorenko@...ux.dev,
	netdev@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH net-next v11 4/5] net: rnpgbe: Add basic mbx_fw support

On Tue, Sep 09, 2025 at 01:58:22PM -0700, Jakub Kicinski wrote:
> On Tue, 9 Sep 2025 19:59:11 +0530 Anwar, Md Danish wrote:
> > > +int mucse_mbx_sync_fw(struct mucse_hw *hw)
> > > +{
> > > +	int try_cnt = 3;
> > > +	int err;
> > > +
> > > +	do {
> > > +		err = mucse_mbx_get_info(hw);
> > > +		if (err == -ETIMEDOUT)
> > > +			continue;
> > > +		break;
> > > +	} while (try_cnt--);
> > > +
> > > +	return err;
> > > +}  
> > 
> > There's a logical issue in the code. The loop structure attempts to
> > retry on ETIMEDOUT errors, but the unconditional break statement after
> > the if-check will always exit the loop after the first attempt,
> > regardless of the error. The do-while loop will never actually retry
> > because the break statement is placed outside of the if condition that
> > checks for timeout errors.
> 

What is expected is 'retry on ETIMEDOUT' and 'no retry others'. 
https://lore.kernel.org/netdev/a066746c-2f12-4e70-b63a-7996392a9132@lunn.ch/

> The other way around. continue; in a do {} while () look does *not*
> evaluate the condition. So this can loop forever.
> 

Maybe I can update like this ?

int mucse_mbx_sync_fw(struct mucse_hw *hw)
{
	int try_cnt = 3;
	int err;

	do {
		err = mucse_mbx_get_info(hw);
		if (err != -ETIMEDOUT)
			break;
		/* only retry with ETIMEDOUT, others just return */
	} while (try_cnt--);

	return err;
}  

Thanks for your feedback.