From: Jens Axboe <axboe@suse.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>
Subject: Re: [patch] fix diskstats_show() accounting with PREEMPT
Date: Wed, 22 Sep 2004 12:55:35 +0200 [thread overview]
Message-ID: <20040922105534.GF2299@suse.de> (raw)
In-Reply-To: <20040921153750.GA21449@elte.hu>
On Tue, Sep 21 2004, Ingo Molnar wrote:
>
> there is another (minor) bug that the smp_processor_id() debugger
> unearthed: diskstats_show() could do a disk_round_stats() ->
> disk_stat_add() with preemption enabled - possibly resulting in losing
> statistics updates.
>
> Patch attached. (The overwhelming majority of disk_stat_add() callers
> have preemption disabled so fixing the remaining two was the best.)
>
> Ingo
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
> --- linux/drivers/block/genhd.c.orig
> +++ linux/drivers/block/genhd.c
> @@ -365,7 +365,9 @@ static ssize_t disk_size_read(struct gen
>
> static ssize_t disk_stats_read(struct gendisk * disk, char *page)
> {
> + preempt_disable();
> disk_round_stats(disk);
> + preempt_enable();
> return sprintf(page,
> "%8u %8u %8llu %8u "
> "%8u %8u %8llu %8u "
> @@ -494,7 +496,9 @@ static int diskstats_show(struct seq_fil
> "\n\n");
> */
>
> + preempt_disable();
> disk_round_stats(gp);
> + preempt_enable();
> seq_printf(s, "%4d %4d %s %u %u %llu %u %u %u %llu %u %u %u %u\n",
> gp->major, n + gp->first_minor, disk_name(gp, n, buf),
> disk_stat_read(gp, reads), disk_stat_read(gp, read_merges),
Looks fine, thanks Ingo.
--
Jens Axboe
prev parent reply other threads:[~2004-09-22 10:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-21 15:37 [patch] fix diskstats_show() accounting with PREEMPT Ingo Molnar
2004-09-22 10:55 ` Jens Axboe [this message]
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