* [patch]raid5: delete another BUG_ON
@ 2014-04-14 6:14 Shaohua Li
2014-04-14 22:47 ` NeilBrown
0 siblings, 1 reply; 3+ messages in thread
From: Shaohua Li @ 2014-04-14 6:14 UTC (permalink / raw)
To: linux-raid, neilb
I hit another BUG_ON with e240c1839d11152b0355442. In __get_priority_stripe(),
stripe count equals to 0 initially. Between atomic_inc and BUG_ON,
get_active_stripe() finds the stripe. So the stripe count isn't 1 any more.
Signed-off-by: Shaohua Li <shli@fusionio.com>
---
drivers/md/raid5.c | 1 -
1 file changed, 1 deletion(-)
Index: linux/drivers/md/raid5.c
===================================================================
--- linux.orig/drivers/md/raid5.c 2014-04-14 11:44:11.448492119 +0800
+++ linux/drivers/md/raid5.c 2014-04-14 11:52:19.158359774 +0800
@@ -4371,7 +4371,6 @@ static struct stripe_head *__get_priorit
}
list_del_init(&sh->lru);
atomic_inc(&sh->count);
- BUG_ON(atomic_read(&sh->count) != 1);
return sh;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch]raid5: delete another BUG_ON
2014-04-14 6:14 [patch]raid5: delete another BUG_ON Shaohua Li
@ 2014-04-14 22:47 ` NeilBrown
2014-04-15 1:12 ` Shaohua Li
0 siblings, 1 reply; 3+ messages in thread
From: NeilBrown @ 2014-04-14 22:47 UTC (permalink / raw)
To: Shaohua Li; +Cc: linux-raid
[-- Attachment #1: Type: text/plain, Size: 993 bytes --]
On Mon, 14 Apr 2014 14:14:17 +0800 Shaohua Li <shli@kernel.org> wrote:
>
> I hit another BUG_ON with e240c1839d11152b0355442. In __get_priority_stripe(),
> stripe count equals to 0 initially. Between atomic_inc and BUG_ON,
> get_active_stripe() finds the stripe. So the stripe count isn't 1 any more.
>
> Signed-off-by: Shaohua Li <shli@fusionio.com>
> ---
> drivers/md/raid5.c | 1 -
> 1 file changed, 1 deletion(-)
>
> Index: linux/drivers/md/raid5.c
> ===================================================================
> --- linux.orig/drivers/md/raid5.c 2014-04-14 11:44:11.448492119 +0800
> +++ linux/drivers/md/raid5.c 2014-04-14 11:52:19.158359774 +0800
> @@ -4371,7 +4371,6 @@ static struct stripe_head *__get_priorit
> }
> list_del_init(&sh->lru);
> atomic_inc(&sh->count);
> - BUG_ON(atomic_read(&sh->count) != 1);
> return sh;
> }
>
What if we made those two lines:
BUG_ON(atomic_inc_return(&sh->count) != 1);
??
NeilBrown
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch]raid5: delete another BUG_ON
2014-04-14 22:47 ` NeilBrown
@ 2014-04-15 1:12 ` Shaohua Li
0 siblings, 0 replies; 3+ messages in thread
From: Shaohua Li @ 2014-04-15 1:12 UTC (permalink / raw)
To: NeilBrown; +Cc: linux-raid
On Tue, Apr 15, 2014 at 08:47:03AM +1000, NeilBrown wrote:
> On Mon, 14 Apr 2014 14:14:17 +0800 Shaohua Li <shli@kernel.org> wrote:
>
> >
> > I hit another BUG_ON with e240c1839d11152b0355442. In __get_priority_stripe(),
> > stripe count equals to 0 initially. Between atomic_inc and BUG_ON,
> > get_active_stripe() finds the stripe. So the stripe count isn't 1 any more.
> >
> > Signed-off-by: Shaohua Li <shli@fusionio.com>
> > ---
> > drivers/md/raid5.c | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > Index: linux/drivers/md/raid5.c
> > ===================================================================
> > --- linux.orig/drivers/md/raid5.c 2014-04-14 11:44:11.448492119 +0800
> > +++ linux/drivers/md/raid5.c 2014-04-14 11:52:19.158359774 +0800
> > @@ -4371,7 +4371,6 @@ static struct stripe_head *__get_priorit
> > }
> > list_del_init(&sh->lru);
> > atomic_inc(&sh->count);
> > - BUG_ON(atomic_read(&sh->count) != 1);
> > return sh;
> > }
> >
>
> What if we made those two lines:
>
> BUG_ON(atomic_inc_return(&sh->count) != 1);
Ok if we want to keep the BUG_ON.
Subject: raid5: fix a race of stripe count check
I hit another BUG_ON with e240c1839d11152b0355442. In __get_priority_stripe(),
stripe count equals to 0 initially. Between atomic_inc and BUG_ON,
get_active_stripe() finds the stripe. So the stripe count isn't 1 any more.
V2: keeps the BUG_ON suggested by Neil.
Signed-off-by: Shaohua Li <shli@fusionio.com>
---
drivers/md/raid5.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
Index: linux/drivers/md/raid5.c
===================================================================
--- linux.orig/drivers/md/raid5.c 2014-04-15 08:17:02.061599785 +0800
+++ linux/drivers/md/raid5.c 2014-04-15 08:18:01.096857614 +0800
@@ -4370,8 +4370,7 @@ static struct stripe_head *__get_priorit
sh->group = NULL;
}
list_del_init(&sh->lru);
- atomic_inc(&sh->count);
- BUG_ON(atomic_read(&sh->count) != 1);
+ BUG_ON(atomic_inc_return(&sh->count) != 1);
return sh;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-04-15 1:12 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-04-14 6:14 [patch]raid5: delete another BUG_ON Shaohua Li
2014-04-14 22:47 ` NeilBrown
2014-04-15 1:12 ` Shaohua Li
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).