Messages in this thread | | | Subject | Re: [BUG] Something goes wrong with timer statistics. | From | Ian Kumlien <> | Date | Fri, 01 Jun 2007 00:59:11 +0200 |
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On tor, 2007-05-31 at 17:27 +0200, Björn Steinbrink wrote: > On 2007.05.31 17:10:07 +0200, Eric Dumazet wrote: > > Well... :) , there is still a memory barrier missing it seems. > > > > Another cpu might see a bad value if 'active=1' is set before tstat_hash_table is really cleared. > > Hm, that even makes the assumption in my first try valid ;-) > Just for the record, this time I thought that the barrier from the > spinlock in timer_stats_update_stats (right before the check for active) > would be enough, but that's obviously running on the wrong cpu if we > race... *sigh* > > Thanks, > Björn > > > > Fix two races in the timer stats lookup code. One by ensuring that the > initialization of a new entry is finished upon insertion of that entry. > The other by cleaning up the hash table when the entries array is > cleared, so that we don't have "pre-inserted" entries. > > Thanks to Eric Dumazet for reminding me of the memory barriers.
Fix the comment below and you can add: Signed-off-by: Ian Kumlien <pomac@vapor.com>
It's currently been running for the longest period ever, ie, 11 minutes =)
I'm gonna leave it running during the night and send a status update when the evil daystar reaches it's peak CET. (i haven't been able to stop since linus mentioned it... damn it... =))
> Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de> > ---
> @@ -360,6 +364,7 @@ static ssize_t tstats_write(struct file *file, const char __user *buf, > if (!active) { > reset_entries(); > time_start = ktime_get(); > + smb_mb();
smb? you mean smp =)
> active = 1; > } > break;
-- Ian Kumlien <pomac () vapor ! com> -- http://pomac.netswarm.net - 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/
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