lkml.org 
[lkml]   [2007]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Fix race with shared tag queue maps


On Thu, 13 Sep 2007, Jens Axboe wrote:
> +
> + /*
> + * Ensure ordering with tag section
> + */
> + smp_mb__before_clear_bit();
> +
> + if (unlikely(!test_and_clear_bit(tag, bqt->tag_map))) {

You don't need the "smp_mb__before_clear_bit()" there.

The regular "clear_bit()" needs it, but the "test_and_xxx()" versions are
architecturally defined to be memory barriers, exactly because they are
regularly used for locking.

This is even documented - see Documentation/atomic_ops.txt.

Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-09-13 17:21    [W:0.048 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site