Re: [PATCH resend 1/3] rtlwifi: rtl8821ae: don't call kfree_skb() under spin_lock_irqsave()

[Yang Yingliang <yangyingliang@huawei.com>]

On 2022/12/7 11:31, Ping-Ke Shih wrote:
>> -----Original Message-----
>> From: Yang Yingliang <yangyingliang@huawei.com>
>> Sent: Tuesday, December 6, 2022 9:13 PM
>> To: Ping-Ke Shih <pkshih@realtek.com>; kvalo@kernel.org
>> Cc: linux-wireless@vger.kernel.org; yangyingliang@huawei.com
>> Subject: [PATCH resend 1/3] rtlwifi: rtl8821ae: don't call kfree_skb() under spin_lock_irqsave()
>>
>> It is not allowed to call kfree_skb() from hardware interrupt
>> context or with interrupts being disabled. So add all skb to
>> a free list, then free them after spin_unlock_irqrestore() at
>> once.
> The patch doesn't change logic, so it should work. But, I would like to know
> if there is a comment about this in kernel code. Could you point it out?
You can see comment of dev_kfree_skb_irq() in include/linux/netdevice.h
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/netdevice.h?h=v6.1-rc8

Thanks,
Yang
>
>> Fixes: 5c99f04fec93 ("rtlwifi: rtl8723be: Update driver to match Realtek release of 06/28/14")
>> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>> ---
>>   drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c
>> b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c
>> index 7e0f62d59fe1..a7e3250957dc 100644
>> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c
>> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c
>> @@ -26,8 +26,10 @@ static void _rtl8821ae_return_beacon_queue_skb(struct ieee80211_hw *hw)
>>   	struct rtl_priv *rtlpriv = rtl_priv(hw);
>>   	struct rtl_pci *rtlpci = rtl_pcidev(rtl_pcipriv(hw));
>>   	struct rtl8192_tx_ring *ring = &rtlpci->tx_ring[BEACON_QUEUE];
>> +	struct sk_buff_head free_list;
>>   	unsigned long flags;
>>
>> +	skb_queue_head_init(&free_list);
>>   	spin_lock_irqsave(&rtlpriv->locks.irq_th_lock, flags);
>>   	while (skb_queue_len(&ring->queue)) {
>>   		struct rtl_tx_desc *entry = &ring->desc[ring->idx];
>> @@ -37,10 +39,12 @@ static void _rtl8821ae_return_beacon_queue_skb(struct ieee80211_hw *hw)
>>   				 rtlpriv->cfg->ops->get_desc(hw, (u8 *)entry,
>>   						true, HW_DESC_TXBUFF_ADDR),
>>   				 skb->len, DMA_TO_DEVICE);
>> -		kfree_skb(skb);
>> +		__skb_queue_tail(&free_list, skb);
>>   		ring->idx = (ring->idx + 1) % ring->entries;
>>   	}
>>   	spin_unlock_irqrestore(&rtlpriv->locks.irq_th_lock, flags);
>> +
>> +	__skb_queue_purge(&free_list);
>>   }
>>
>>   static void _rtl8821ae_set_bcn_ctrl_reg(struct ieee80211_hw *hw,
>> --
>> 2.25.1
>>
>>
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> .