netdev - RE: [RFC/PATCH] net: add deferred flow cache flush function to be used in xfrm

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Date:	Mon, 12 Sep 2011 14:37:36 +0000
From:	Bucur Madalin-Cristian-B32716 <B32716@...escale.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"timo.teras@....fi" <timo.teras@....fi>
Subject: RE: [RFC/PATCH] net: add deferred flow cache flush function to be
 used in xfrm

> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On
> Behalf Of Eric Dumazet
> Sent: Monday, September 12, 2011 4:58 PM
> 
> Le lundi 12 septembre 2011 à 15:17 +0300, Madalin Bucur a écrit :
> > The xfrm garbage collector calls flow_cache_flush() that might sleep.
> > The xfrm garbage collector can be called from softirq context, such as from
> > net_rx_action() through ip_forward(). Added flow_cache_flush_deferred()
> > function that uses the kernel-global work queue to leave the actual
> > cache flush processing outside the softirq context.
> >
> 
> Problem is sometime we dont want to defer and are in process context.
> 
> xfrm_dev_event(  event == NETDEV_DOWN) is probably a place we dont want
> to defer the garbage collection.
> 

Indeed, currently __xfrm_garbage_collect() is called through the garbage_collect
callback but also when an event NETDEV_DOWN is received. Maybe we should have
different functions for the two cases, one calling flow_cache_flush_deferred()
and the other flow_cache_flush().