linux-kernel - Re: sk_lock: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM

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Message-ID: <20090715074503.GC6145@localhost>
Date:	Wed, 15 Jul 2009 15:45:03 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	David Miller <davem@...emloft.net>
Cc:	"herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: sk_lock: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W}
	usage

On Wed, Jul 15, 2009 at 12:04:32AM +0800, David Miller wrote:
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Date: Fri, 10 Jul 2009 16:02:47 +0800
> 
> > On Fri, Jul 10, 2009 at 04:00:17PM +0800, Wu Fengguang wrote:
> >> 
> >> The (sk_allocation & ~__GFP_WAIT) cases should be rare, but I guess
> >> the networking code shall do it anyway, because sk_allocation defaults
> >> to GFP_KERNEL. It seems that currently the networking code simply uses
> >> a lot of GFP_ATOMIC, do they really mean "I cannot sleep"?
> > 
> > Yep because they're done from softirq context.
> 
> Yes, this is the core issue.

Yes, that's general true. But..

> All of Wu's talk about how "GFP_ATOMIC will wake up kswapd and
> therefore can succeed just as well as GFP_KERNEL" is not relevant,
> because GFP_ATOMIC means sleeping is not allowed.

We are talking about tcp_send_fin() here, which can sleep.

Thanks,
Fengguang
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