linux-kernel - Re: [PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue

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Message-ID: <20250805181446.3deaceb9@kernel.org>
Date: Tue, 5 Aug 2025 18:14:46 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Jijie Shao <shaojijie@...wei.com>
Cc: <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
 <andrew+netdev@...n.ch>, <horms@...nel.org>, <shenjian15@...wei.com>,
 <liuyonglong@...wei.com>, <chenhao418@...wei.com>,
 <jonathan.cameron@...wei.com>, <shameerali.kolothum.thodi@...wei.com>,
 <salil.mehta@...wei.com>, <netdev@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue

On Sat, 2 Aug 2025 20:32:25 +0800 Jijie Shao wrote:
>  static inline u32 hbg_get_queue_used_num(struct hbg_ring *ring)
>  {
> +	if (!ring->len)
> +		return 0;
> +
>  	return (ring->ntu + ring->len - ring->ntc) % ring->len;

This should probably be a READ_ONCE() to a temporary variable.
There is no locking in debugfs, AFAICT, the value may change
between the test and the division / modulo.
-- 
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