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From: Peter Zijlstra <peterz@infradead.org>
To: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH -mm 1/2] irq_work, Use llist in irq_work
Date: Thu, 01 Sep 2011 12:00:01 +0200	[thread overview]
Message-ID: <1314871201.7945.17.camel@twins> (raw)
In-Reply-To: <4E5F45F6.70009@intel.com>

On Thu, 2011-09-01 at 16:44 +0800, Huang Ying wrote:

> Because llist is in library, it may be used in highly contended case and
> light/un-contended loads.  So maybe code as above is best choice for llist.

Well the thing is, if you're heavily contended you should probably be
doing something else..

> > Also, just noticed, why do you have different list_head/list_node
> > structures? They're the same, a single pointer.
> 
> There is only one structure before (llist_head).  Linus give me some
> comments about that, suggests to use 2 structures.  I think his comments
> are reasonable.  Copied here:

OK

> Even with this_cpu_* ops, it seems that the race condition I described
> is still possible.
> 
> - use this_cpu_cmpxchg to queue irq_work into irq_work_list of CPU A
> - preempted and resumed execution on CPU B
> - arch_irq_work_raise on CPU B
> 
> Do you think so?

No you're right, got my brain inside-out today or so..

  reply	other threads:[~2011-09-01 10:00 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-30  5:16 [PATCH -mm 0/2] Use llist in irq_work and xlist Huang Ying
2011-08-30  5:16 ` [PATCH -mm 1/2] irq_work, Use llist in irq_work Huang Ying
2011-08-31 10:10   ` Peter Zijlstra
2011-09-01  1:46     ` Huang Ying
2011-09-01  3:20       ` Huang Ying
2011-09-01  7:58         ` Peter Zijlstra
2011-09-01  8:56           ` Huang Ying
2011-09-01  9:57             ` Peter Zijlstra
2011-09-02  1:14               ` Huang Ying
2011-09-03 17:35                 ` Mathieu Desnoyers
2011-09-01 12:51             ` Mathieu Desnoyers
2011-09-01 13:00               ` Mathieu Desnoyers
2011-09-02  1:08               ` Huang Ying
2011-09-03 16:33                 ` Mathieu Desnoyers
2011-09-01  7:57       ` Peter Zijlstra
2011-09-01  8:44         ` Huang Ying
2011-09-01 10:00           ` Peter Zijlstra [this message]
2011-09-02  1:18             ` Huang Ying
2011-09-02 13:26               ` Peter Zijlstra
2011-08-30  5:16 ` [PATCH -mm 2/2] net, rds, Replace xlist in net/rds/xlist.h with llist Huang Ying

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