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Subject: Re: [PATCH V2 net 2/3] net: hibmcge: fix the division by zero issue
To: Jakub Kicinski <kuba@kernel.org>
References: <20250802123226.3386231-1-shaojijie@huawei.com>
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From: Jijie Shao <shaojijie@huawei.com>
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on 2025/8/6 9:14, Jakub Kicinski wrote:
> 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.

Yes, there is indeed a very short time window.
I will add READ_ONCE() to ring->len and read it only once.

Thanks
Jijie Shao