netdev - Re: tun: Use netif_receive_skb instead of netif

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100519082047.GA24331@gondor.apana.org.au>
Date:	Wed, 19 May 2010 18:20:47 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Thomas Graf <tgraf@...hat.com>,
	Neil Horman <nhorman@...hat.com>, netdev@...r.kernel.org
Subject: Re: tun: Use netif_receive_skb instead of netif_rx

On Wed, May 19, 2010 at 10:09:42AM +0200, Eric Dumazet wrote:
> 
> 6) netif_rx() pro is that packet processing is done while stack usage is
> guaranteed to be low (from process_backlog, using a special softirq
> stack, instead of current stack)
> 
> After your patch, tun will use more stack. Is it safe on all contexts ?

Dave also raised this but I believe nothing changes with regards
to the stack.  We currently call do_softirq which does not switch
stacks.

Only a real interrupt would switch stacks.

> Another concern I have is about RPS.
> 
> netif_receive_skb() must be called from process_backlog() context, or
> there is no guarantee the IPI will be sent if this skb is enqueued for
> another cpu.

Can you explain this a bit more?

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html