linux-kernel - Re: [PATCH] NOHZ: local_softirq

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Message-ID: <Pine.LNX.4.64.0705171453580.31321@artax.karlin.mff.cuni.cz>
Date:	Thu, 17 May 2007 15:05:34 +0200 (CEST)
From:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] NOHZ: local_softirq_pending with tickless plip

>> Hi
>>
>> On one of my machines with tickless kernel and plip I get messages :
>
> I bet this is a machine a P4 with Hyperthreading enabled ?

No, it's single Pentium 2. I have other Pentium MMX using plip, where I 
don't get these error messages, I don't know why.

Mikulas

>> NOHZ: local_softirq_pending 08
>>
>> always when using plip (on other machine with tickless kernel and plip I
>> get no errors). Thebug happens both on 2.6.21 and 2.6.22-rc1
>>
>> This patch fixes that. Note that plip calls netif_rx neither from hardware
>> interrupt nor from ksoftirqd, so there is no one who would wake
>> ksoftirqd then. netif_tx calls only
>> __raise_softirq_irqoff(NET_RX_SOFTIRQ), which sets softirq bit, but
>> doesn't wake ksoftirqd.
>
> Dave,
>
> can we please get rid of __raise_softirq_irqoff() at all ? These micro
> optimizations are causing more trouble than they are worth.
>
> 	tglx
>
>> Mikulas
>>
>> Signed-off-by: Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz
>>
>> --- linux-2.6.22-rc1/net/core/dev.c_	Fri May 18 07:51:01 2007
>> +++ linux-2.6.22-rc1/net/core/dev.c	Fri May 18 07:51:06 2007
>> @@ -1117,7 +1117,7 @@
>>   		dev->quota += dev->weight;
>>   	else
>>   		dev->quota = dev->weight;
>> -	__raise_softirq_irqoff(NET_RX_SOFTIRQ);
>> +	raise_softirq_irqoff(NET_RX_SOFTIRQ);
>>   	local_irq_restore(flags);
>>   }
>>   EXPORT_SYMBOL(__netif_rx_schedule);
>
>
-
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