linux-kernel - Re: [PATCH 06/33] mm: allow PF

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Date:	Wed, 31 Oct 2007 14:06:29 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	netdev@...r.kernel.org, trond.myklebust@....uio.no
Subject: Re: [PATCH 06/33] mm: allow PF_MEMALLOC from softirq context

On Wed, 2007-10-31 at 21:49 +1100, Nick Piggin wrote:
> On Wednesday 31 October 2007 21:42, Peter Zijlstra wrote:
> > On Wed, 2007-10-31 at 14:51 +1100, Nick Piggin wrote:
> > > On Wednesday 31 October 2007 03:04, Peter Zijlstra wrote:
> > > > Allow PF_MEMALLOC to be set in softirq context. When running softirqs
> > > > from a borrowed context save current->flags, ksoftirqd will have its
> > > > own task_struct.
> > >
> > > What's this for? Why would ksoftirqd pick up PF_MEMALLOC? (I guess
> > > that some networking thing must be picking it up in a subsequent patch,
> > > but I'm too lazy to look!)... Again, can you have more of a rationale in
> > > your patch headers, or ref the patch that uses it... thanks
> >
> > Right, I knew I was forgetting something in these changelogs.
> >
> > The network stack does quite a bit of packet processing from softirq
> > context. Once you start swapping over network, some of the packets want
> > to be processed under PF_MEMALLOC.
> 
> Hmm... what about processing from interrupt context?

From what I could tell that is not done, ISR just fills the skb and
sticks it on an RX queue to be further processed by the softirq.

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