* [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle
@ 2017-08-07 5:50 Neeraj Upadhyay
2017-08-07 12:40 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Neeraj Upadhyay @ 2017-08-07 5:50 UTC (permalink / raw)
To: paulmck, josh, rostedt, mathieu.desnoyers, jiangshanlai
Cc: linux-kernel, Neeraj Upadhyay
Pending cbs check in rcu_prepare_for_idle is inversed
in the sense that, it should accelerate if there are
pending cbs; but, the check does the opposite. So,
fix it.
Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
---
kernel/rcu/tree_plugin.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 908b309..b8f51df 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
rdtp->last_accelerate = jiffies;
for_each_rcu_flavor(rsp) {
rdp = this_cpu_ptr(rsp->rda);
- if (rcu_segcblist_pend_cbs(&rdp->cblist))
+ if (!rcu_segcblist_pend_cbs(&rdp->cblist))
continue;
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle
2017-08-07 5:50 [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle Neeraj Upadhyay
@ 2017-08-07 12:40 ` Paul E. McKenney
2017-08-07 14:01 ` Neeraj Upadhyay
0 siblings, 1 reply; 4+ messages in thread
From: Paul E. McKenney @ 2017-08-07 12:40 UTC (permalink / raw)
To: Neeraj Upadhyay
Cc: josh, rostedt, mathieu.desnoyers, jiangshanlai, linux-kernel
On Mon, Aug 07, 2017 at 11:20:10AM +0530, Neeraj Upadhyay wrote:
> Pending cbs check in rcu_prepare_for_idle is inversed
> in the sense that, it should accelerate if there are
> pending cbs; but, the check does the opposite. So,
> fix it.
>
> Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Good catch! Queued for review and testing.
Just out of curiosity, how did you find this one?
Thanx, Paul
> ---
> kernel/rcu/tree_plugin.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 908b309..b8f51df 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
> rdtp->last_accelerate = jiffies;
> for_each_rcu_flavor(rsp) {
> rdp = this_cpu_ptr(rsp->rda);
> - if (rcu_segcblist_pend_cbs(&rdp->cblist))
> + if (!rcu_segcblist_pend_cbs(&rdp->cblist))
> continue;
> rnp = rdp->mynode;
> raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> member of the Code Aurora Forum, hosted by The Linux Foundation
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle
2017-08-07 12:40 ` Paul E. McKenney
@ 2017-08-07 14:01 ` Neeraj Upadhyay
2017-08-07 14:09 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Neeraj Upadhyay @ 2017-08-07 14:01 UTC (permalink / raw)
To: paulmck; +Cc: josh, rostedt, mathieu.desnoyers, jiangshanlai, linux-kernel
On 08/07/2017 06:10 PM, Paul E. McKenney wrote:
> On Mon, Aug 07, 2017 at 11:20:10AM +0530, Neeraj Upadhyay wrote:
>> Pending cbs check in rcu_prepare_for_idle is inversed
>> in the sense that, it should accelerate if there are
>> pending cbs; but, the check does the opposite. So,
>> fix it.
>>
>> Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
>> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
> Good catch! Queued for review and testing.
>
> Just out of curiosity, how did you find this one?
>
> Thanx, Paul
Hi Paul, found the issue while reading the code.
>
>> ---
>> kernel/rcu/tree_plugin.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
>> index 908b309..b8f51df 100644
>> --- a/kernel/rcu/tree_plugin.h
>> +++ b/kernel/rcu/tree_plugin.h
>> @@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
>> rdtp->last_accelerate = jiffies;
>> for_each_rcu_flavor(rsp) {
>> rdp = this_cpu_ptr(rsp->rda);
>> - if (rcu_segcblist_pend_cbs(&rdp->cblist))
>> + if (!rcu_segcblist_pend_cbs(&rdp->cblist))
>> continue;
>> rnp = rdp->mynode;
>> raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
>> --
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
>> member of the Code Aurora Forum, hosted by The Linux Foundation
>>
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle
2017-08-07 14:01 ` Neeraj Upadhyay
@ 2017-08-07 14:09 ` Paul E. McKenney
0 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2017-08-07 14:09 UTC (permalink / raw)
To: Neeraj Upadhyay
Cc: josh, rostedt, mathieu.desnoyers, jiangshanlai, linux-kernel
On Mon, Aug 07, 2017 at 07:31:27PM +0530, Neeraj Upadhyay wrote:
>
>
> On 08/07/2017 06:10 PM, Paul E. McKenney wrote:
> >On Mon, Aug 07, 2017 at 11:20:10AM +0530, Neeraj Upadhyay wrote:
> >>Pending cbs check in rcu_prepare_for_idle is inversed
> >>in the sense that, it should accelerate if there are
> >>pending cbs; but, the check does the opposite. So,
> >>fix it.
> >>
> >>Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
> >>Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
> >Good catch! Queued for review and testing.
> >
> >Just out of curiosity, how did you find this one?
>
> Hi Paul, found the issue while reading the code.
Very good, and please feel free to continue reading and finding more
bugs! ;-)
Thanx, Paul
> >>---
> >> kernel/rcu/tree_plugin.h | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >>diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> >>index 908b309..b8f51df 100644
> >>--- a/kernel/rcu/tree_plugin.h
> >>+++ b/kernel/rcu/tree_plugin.h
> >>@@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
> >> rdtp->last_accelerate = jiffies;
> >> for_each_rcu_flavor(rsp) {
> >> rdp = this_cpu_ptr(rsp->rda);
> >>- if (rcu_segcblist_pend_cbs(&rdp->cblist))
> >>+ if (!rcu_segcblist_pend_cbs(&rdp->cblist))
> >> continue;
> >> rnp = rdp->mynode;
> >> raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
> >>--
> >>QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> >>member of the Code Aurora Forum, hosted by The Linux Foundation
> >>
>
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> member of the Code Aurora Forum, hosted by The Linux Foundation
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-08-07 5:50 [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle Neeraj Upadhyay
2017-08-07 12:40 ` Paul E. McKenney
2017-08-07 14:01 ` Neeraj Upadhyay
2017-08-07 14:09 ` Paul E. McKenney
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