* [patch] fix diskstats_show() accounting with PREEMPT
@ 2004-09-21 15:37 Ingo Molnar
2004-09-22 10:55 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Ingo Molnar @ 2004-09-21 15:37 UTC (permalink / raw)
To: Jens Axboe; +Cc: linux-kernel, Andrew Morton
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),
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [patch] fix diskstats_show() accounting with PREEMPT
2004-09-21 15:37 [patch] fix diskstats_show() accounting with PREEMPT Ingo Molnar
@ 2004-09-22 10:55 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2004-09-22 10:55 UTC (permalink / raw)
To: Ingo Molnar; +Cc: linux-kernel, Andrew Morton
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
^ permalink raw reply [flat|nested] 2+ messages in thread
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2004-09-21 15:37 [patch] fix diskstats_show() accounting with PREEMPT Ingo Molnar
2004-09-22 10:55 ` Jens Axboe
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