linux-kernel - Re: [rfc] direct IO submission and completion scalability issues

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Message-ID: <84144f020802030253y596ca557w3a44a8601a13596d@mail.gmail.com>
Date:	Sun, 3 Feb 2008 12:53:02 +0200
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Nick Piggin" <npiggin@...e.de>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	linux-kernel@...r.kernel.org, arjan@...ux.intel.com, mingo@...e.hu,
	ak@...e.de, jens.axboe@...cle.com, James.Bottomley@...eleye.com,
	andrea@...e.de, clameter@....com, akpm@...ux-foundation.org,
	andrew.vasquez@...gic.com, willy@...ux.intel.com,
	"Zach Brown" <zach.brown@...cle.com>
Subject: Re: [rfc] direct IO submission and completion scalability issues

Hi Nick,

On Feb 3, 2008 11:52 AM, Nick Piggin <npiggin@...e.de> wrote:
> +asmlinkage void smp_call_function_fast_interrupt(void)
> +{

[snip]

> +       while (!list_empty(&list)) {
> +               struct call_single_data *data;
> +
> +               data = list_entry(list.next, struct call_single_data, list);
> +               list_del(&data->list);
> +
> +               data->func(data->info);
> +               if (data->wait) {
> +                       smp_mb();
> +                       data->wait = 0;

Why do we need smp_mb() here (maybe add a comment to keep
Andrew/checkpatch happy)?

                        Pekka
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