[PATCH] srcu: Fix incorrect condition in srcu_funnel_exp_start()

[PATCH] srcu: Fix incorrect condition in srcu_funnel_exp_start()

[Byungchul Park]

We should've kept sp->srcu_gp_seq_needed_exp the furthest. But
it probably fails because of the incorrect condition. Fix it.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 kernel/rcu/srcutree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index d5cea81..44bc0fa 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -626,7 +626,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp,
 		spin_unlock_irqrestore_rcu_node(snp, flags);
 	}
 	spin_lock_irqsave_rcu_node(sp, flags);
-	if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
+	if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
 		sp->srcu_gp_seq_needed_exp = s;
 	spin_unlock_irqrestore_rcu_node(sp, flags);
 }
-- 
1.9.1

Re: [PATCH] srcu: Fix incorrect condition in srcu_funnel_exp_start()

[Paul E. McKenney]

On Wed, Feb 14, 2018 at 05:59:54PM +0900, Byungchul Park wrote:
> We should've kept sp->srcu_gp_seq_needed_exp the furthest. But
> it probably fails because of the incorrect condition. Fix it.
> 
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>

Good catch, and thank you for reviewing the SRCU code, but Ildar Ismagilov
beat you to this one.  Please see 574428dee1f3 ("rcu: Fix misprint in
srcu_funnel_exp_start") in -rcu.

							Thanx, Paul

> ---
>  kernel/rcu/srcutree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index d5cea81..44bc0fa 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -626,7 +626,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp,
>  		spin_unlock_irqrestore_rcu_node(snp, flags);
>  	}
>  	spin_lock_irqsave_rcu_node(sp, flags);
> -	if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
> +	if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
>  		sp->srcu_gp_seq_needed_exp = s;
>  	spin_unlock_irqrestore_rcu_node(sp, flags);
>  }
> -- 
> 1.9.1
> 

Re: [PATCH] srcu: Fix incorrect condition in srcu_funnel_exp_start()

[Byungchul Park]

On 2/15/2018 6:42 AM, Paul E. McKenney wrote:
> On Wed, Feb 14, 2018 at 05:59:54PM +0900, Byungchul Park wrote:
>> We should've kept sp->srcu_gp_seq_needed_exp the furthest. But
>> it probably fails because of the incorrect condition. Fix it.
>>
>> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> 
> Good catch, and thank you for reviewing the SRCU code, but Ildar Ismagilov
> beat you to this one.  Please see 574428dee1f3 ("rcu: Fix misprint in
> srcu_funnel_exp_start") in -rcu.

Hi Paul,

I'm sorry I'm late. It's been Lunar New Year holiday since last
thursday.

Do you mean:

git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

Is this rcu's main dev-tree?

Thanks for replying anyway, and happy new year~

> 
> 							Thanx, Paul
> 
>> ---
>>   kernel/rcu/srcutree.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
>> index d5cea81..44bc0fa 100644
>> --- a/kernel/rcu/srcutree.c
>> +++ b/kernel/rcu/srcutree.c
>> @@ -626,7 +626,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp,
>>   		spin_unlock_irqrestore_rcu_node(snp, flags);
>>   	}
>>   	spin_lock_irqsave_rcu_node(sp, flags);
>> -	if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
>> +	if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
>>   		sp->srcu_gp_seq_needed_exp = s;
>>   	spin_unlock_irqrestore_rcu_node(sp, flags);
>>   }
>> -- 
>> 1.9.1
>>
> 
> 

-- 
Thanks,
Byungchul

Re: [PATCH] srcu: Fix incorrect condition in srcu_funnel_exp_start()

[Paul E. McKenney]

On Mon, Feb 19, 2018 at 08:36:30AM +0900, Byungchul Park wrote:
> On 2/15/2018 6:42 AM, Paul E. McKenney wrote:
> >On Wed, Feb 14, 2018 at 05:59:54PM +0900, Byungchul Park wrote:
> >>We should've kept sp->srcu_gp_seq_needed_exp the furthest. But
> >>it probably fails because of the incorrect condition. Fix it.
> >>
> >>Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> >
> >Good catch, and thank you for reviewing the SRCU code, but Ildar Ismagilov
> >beat you to this one.  Please see 574428dee1f3 ("rcu: Fix misprint in
> >srcu_funnel_exp_start") in -rcu.
> 
> Hi Paul,
> 
> I'm sorry I'm late. It's been Lunar New Year holiday since last
> thursday.

Not a problem!

> Do you mean:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> 
> Is this rcu's main dev-tree?

It is indeed!

> Thanks for replying anyway, and happy new year~

And a very happy Lunar New Year to you and yours!!!

							Thanx, Paul

> >>---
> >>  kernel/rcu/srcutree.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >>diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> >>index d5cea81..44bc0fa 100644
> >>--- a/kernel/rcu/srcutree.c
> >>+++ b/kernel/rcu/srcutree.c
> >>@@ -626,7 +626,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp,
> >>  		spin_unlock_irqrestore_rcu_node(snp, flags);
> >>  	}
> >>  	spin_lock_irqsave_rcu_node(sp, flags);
> >>-	if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
> >>+	if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s))
> >>  		sp->srcu_gp_seq_needed_exp = s;
> >>  	spin_unlock_irqrestore_rcu_node(sp, flags);
> >>  }
> >>-- 
> >>1.9.1
> >>
> >
> >
> 
> -- 
> Thanks,
> Byungchul
>