2022-05-25 09:08:10

by Zqiang

Subject: [PATCH] rcu: Fix incorrect judgment condition in show_rcu_nocb_state()

When check the 'rdp->nocb_cb_kthread' tasks exists, if is true, however
the output is the cpu where 'rdp->nocb_gp_kthread' is located. this
ensure that the tasks in the judgment condition and the tasks of the
cpu where the output tasks are located are the same tasks.

Signed-off-by: Zqiang <[email protected]>
---
kernel/rcu/tree_nocb.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index fa8e4f82e60c..f4ee81d119c8 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1438,8 +1438,8 @@ static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
(long)rdp->nocb_gp_seq,
rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
- show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+ rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
}

/* Dump out nocb kthread state for the specified rcu_data structure. */
@@ -1483,7 +1483,7 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
rcu_segcblist_n_cbs(&rdp->cblist),
rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));

/* It is OK for GP kthreads to have GP state. */
--
2.25.1

2022-05-25 13:03:40

by Mukesh Ojha

Subject: Re: [PATCH] rcu: Fix incorrect judgment condition in show_rcu_nocb_state()

On 5/25/2022 9:04 AM, Zqiang wrote:
> When check the 'rdp->nocb_cb_kthread' tasks exists, if is true, however
> the output is the cpu where 'rdp->nocb_gp_kthread' is located. this
> ensure that the tasks in the judgment condition and the tasks of the
> cpu where the output tasks are located are the same tasks.
>
> Signed-off-by: Zqiang <[email protected]>
> ---
> kernel/rcu/tree_nocb.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> index fa8e4f82e60c..f4ee81d119c8 100644
> --- a/kernel/rcu/tree_nocb.h
> +++ b/kernel/rcu/tree_nocb.h
> @@ -1438,8 +1438,8 @@ static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
> (long)rdp->nocb_gp_seq,
> rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
> rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
> - rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> - show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
> + rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> + show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
> }
>
> /* Dump out nocb kthread state for the specified rcu_data structure. */
> @@ -1483,7 +1483,7 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
> ".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
> rcu_segcblist_n_cbs(&rdp->cblist),
> rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
> - rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> + rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
> show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
>

Nice !!
Reviewed-by: [email protected]

-Mukesh

> /* It is OK for GP kthreads to have GP state. */

2022-06-01 21:22:29

by Zqiang

Subject: RE: [PATCH] rcu: Fix incorrect judgment condition in show_rcu_nocb_state()

Hi Frederic

Friendly ping.

Thanks
Zqiang


When check the 'rdp->nocb_cb_kthread' tasks exists, if is true, however
the output is the cpu where 'rdp->nocb_gp_kthread' is located. this
ensure that the tasks in the judgment condition and the tasks of the
cpu where the output tasks are located are the same tasks.

Signed-off-by: Zqiang <[email protected]>
---
kernel/rcu/tree_nocb.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index fa8e4f82e60c..f4ee81d119c8 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1438,8 +1438,8 @@ static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
(long)rdp->nocb_gp_seq,
rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
- show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+ rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
}

/* Dump out nocb kthread state for the specified rcu_data structure. */
@@ -1483,7 +1483,7 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
rcu_segcblist_n_cbs(&rdp->cblist),
rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
- rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));

/* It is OK for GP kthreads to have GP state. */
--
2.25.1