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From: Cong Wang <amwang@redhat.com>
To: netdev@vger.kernel.org
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Sylvain Munaut <s.munaut@whatever-company.com>,
	David Miller <davem@davemloft.net>
Subject: Q: what protects dev->napi_list?
Date: Fri, 24 Aug 2012 17:46:44 +0800	[thread overview]
Message-ID: <1345801604.11584.24.camel@cr0> (raw)

Hi,

Sylvain reported a netpoll CPU stall
http://marc.info/?l=linux-netdev&m=134563282530588&w=2

I tried to provide some fix for it:
http://marc.info/?l=linux-netdev&m=134571069921429&w=2

When reviewing that code, I noticed a problem, it seems dev->napi_list
is not protected by any lock? What if the device driver calls
netif_napi_del() meanwhile we are iterating &dev->napi_list in
poll_napi()? It seems netif_napi_del()/netif_napi_add() are usually
called with the RTNL lock held during driver init/uninit, but again
poll_napi() doesn't have RTNL lock.

Am I missing anything?

Thanks!

             reply	other threads:[~2012-08-24  9:46 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-24  9:46 Cong Wang [this message]
2012-08-24 10:12 ` Q: what protects dev->napi_list? Eric Dumazet
2012-08-24 10:39   ` Cong Wang
2012-08-24 11:29     ` Eric Dumazet
2012-08-25  6:08       ` Cong Wang
2012-08-25  6:49         ` Eric Dumazet

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