linux-kernel - Re: [Softirq] a76eadba0d: WARNING:at_net/mac80211/rx.c:#ieee80211_rx

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Date:   Thu, 23 Jul 2020 16:35:55 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     jun qian <qianjun.kernel@...il.com>
Cc:     kernel test robot <lkp@...el.com>, peterz@...radead.org,
        will@...nel.org, luto@...nel.org, linux-kernel@...r.kernel.org,
        Uladzislau Rezki <urezki@...il.com>,
        Yafang Shao <laoar.shao@...il.com>, lkp@...ts.01.org
Subject: Re: [Softirq] a76eadba0d: WARNING:at_net/mac80211/rx.c:#ieee80211_rx_napi[mac80211]

jun qian <qianjun.kernel@...il.com> writes:
> On Thu, Jul 23, 2020 at 6:58 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>> That drops everything which has not yet been processed and the above
>> warning is due to this.
>>
> wow, I made a mistake, thank you for finding the cause of the problem
> so quickly.
>
> How about the following code.   we need to clear the corresponding
> pending bit at the
> right time Instead of all the pending bits cleared in the start.
>
> pending = softirq_pending();
>
> while ((softirq_bit = ffs(pending))) {
>
>         pending >>= softirq_bit;
>
>         set_softirq_pending(pending);  //Only clear the corresponding
> bit which will be processed.

How is that supposed to be correct. pending has been shifted
right. Something like this should work:

 		h++;
 		pending >>= softirq_bit;

		if (timeout()) {
			/*
			 * Ensure that the remaining pending bits
			 * are handled.
			 */
			or_softirq_pending(pending << (vec_nr + 1));
			break;
		}
 	}

Thanks,

        tglx