netdev - RE: NAPI rescheduling and the delay caused by it

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Date:	Mon, 09 Dec 2013 17:17:40 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Zoltan Kiss <zoltan.kiss@...rix.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	Malcolm Crossley <malcolm.crossley@...rix.com>,
	Jonathan Davies <Jonathan.Davies@...rix.com>,
	Paul Durrant <Paul.Durrant@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: RE: NAPI rescheduling and the delay caused by it

On Mon, 2013-12-09 at 17:14 -0800, Eric Dumazet wrote:

> > I found another suspect however: my grant mapping patches do the
> > unmapping from the NAPI instance where otherwise we receive the
> > packets from the guest. But this means we call napi_schedule from the
> > zerocopy callback, which can be run by anyone who free up that skb,
> > including an another VIF's RX thread (which actually does the transmit
> > TO the guest). I guess that might be bad.
> 
> Same problem : napi_schedule() is meant to be used from interrupt
> context.
> 

Check commit ec13ee80145ccb95b00e6e610044bbd94a170051
for example.



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