Re: [PATCH] net: cpu offline cause napi stall

[David Miller <davem@davemloft.net>]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 07 Jun 2011 08:50:03 +0200

> From: Heiko Carstens <heiko.carstens@de.ibm.com>
> 
> Frank Blaschka reported :
> <quote>
>   During heavy network load we turn off/on cpus.
>   Sometimes this causes a stall on the network device.
>   Digging into the dump I found out following:
> 
>   napi is scheduled but does not run. From the I/O buffers
>   and the napi state I see napi/rx_softirq processing has stopped
>   because the budget was reached. napi stays in the
>   softnet_data poll_list and the rx_softirq was raised again.
> 
>   I assume at this time the cpu offline comes in,
>   the rx softirq is raised/moved to another cpu but napi stays in the
>   poll_list of the softnet_data of the now offline cpu.
> 
>   Reviewing dev_cpu_callback (net/core/dev.c) I did not find the
>   poll_list is transfered to the new cpu.
> </quote>
> 
> This patch is a straightforward implementation of Frank suggestion :
> 
> Transfert poll_list and trigger NET_RX_SOFTIRQ on new cpu.
> 
> Reported-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> Tested-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied, thanks everyone.