linux-kernel - Re: [rfc/rft][patch] should use scheduler sync hint in tcp

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Message-ID: <20100304030300.GE23633@elte.hu>
Date:	Thu, 4 Mar 2010 04:03:00 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	eric.dumazet@...il.com, efault@....de, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [rfc/rft][patch] should use scheduler sync hint in
 tcp_prequeue()?


* David Miller <davem@...emloft.net> wrote:

> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Tue, 02 Mar 2010 12:27:53 +0100
> 
> > Le mardi 02 mars 2010 ? 10:41 +0100, Mike Galbraith a ?crit :
> >> diff --git a/include/net/tcp.h b/include/net/tcp.h
> >> index 34f5cc2..ba3fc64 100644
> >> --- a/include/net/tcp.h
> >> +++ b/include/net/tcp.h
> >> @@ -939,7 +939,7 @@ static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
> >>  
> >>  		tp->ucopy.memory = 0;
> >>  	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
> >> -		wake_up_interruptible_poll(sk->sk_sleep,
> >> +		wake_up_interruptible_sync_poll(sk->sk_sleep,
> >>  					   POLLIN | POLLRDNORM | POLLRDBAND);
> >>  		if (!inet_csk_ack_scheduled(sk))
> >>  			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
> >> 
>  ...
> > Ingo probably can answer to this question, since he changed
> > sock_def_readable() (and others) in commit 6f3d09291b498299
> > I suspect he missed tcp_prequeue() case, maybe not...
> 
> It definitely looks like an oversight to me and we should add
> be using wake_up_interruptible_sync_poll() in tcp_prequeue()
> as above.
> 
> Ingo?

Yeah. I remember that patch, it was minimalistic, based on the workload i 
could trigger back then.

Thanks,

	Ingo
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