2018-10-08 06:51:22

by Zhouyi Zhou

Subject: [PATCH] RCU: Adjust the comment of function rcu_is_watching

From: Zhouyi Zhou <[email protected]>

Because RCU avoids interrupting idle CPUs, rcu_is_watching is used to
test whether or not it is currently legal to run RCU read-side
critical sections on this CPU.

First sentence and last sentence of current comment for rcu_is_watching
have opposite meaning of what is expected.

Signed-off-by: Zhouyi Zhou <[email protected]>
---
kernel/rcu/tree.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0b760c1..adb04ea 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1010,12 +1010,12 @@ void rcu_irq_enter_irqson(void)
}

/**
- * rcu_is_watching - see if RCU thinks that the current CPU is idle
+ * rcu_is_watching - see if RCU thinks that the current CPU is not idle
*
* Return true if RCU is watching the running CPU, which means that this
* CPU can safely enter RCU read-side critical sections. In other words,
- * if the current CPU is in its idle loop and is neither in an interrupt
- * or NMI handler, return true.
+ * if the current CPU is not in its idle loop or is in an interrupt or
+ * NMI handler, return true.
*/
bool notrace rcu_is_watching(void)
{
--
2.1.4

2018-10-09 04:06:24

by Paul E. McKenney

Subject: Re: [PATCH] RCU: Adjust the comment of function rcu_is_watching

On Mon, Oct 08, 2018 at 06:50:41AM +0000, [email protected] wrote:
> From: Zhouyi Zhou <[email protected]>
>
> Because RCU avoids interrupting idle CPUs, rcu_is_watching is used to
> test whether or not it is currently legal to run RCU read-side
> critical sections on this CPU.
>
> First sentence and last sentence of current comment for rcu_is_watching
> have opposite meaning of what is expected.
>
> Signed-off-by: Zhouyi Zhou <[email protected]>

Good eyes! Applied and pushed, thank you!

Thanx, Paul

> ---
> kernel/rcu/tree.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 0b760c1..adb04ea 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1010,12 +1010,12 @@ void rcu_irq_enter_irqson(void)
> }
>
> /**
> - * rcu_is_watching - see if RCU thinks that the current CPU is idle
> + * rcu_is_watching - see if RCU thinks that the current CPU is not idle
> *
> * Return true if RCU is watching the running CPU, which means that this
> * CPU can safely enter RCU read-side critical sections. In other words,
> - * if the current CPU is in its idle loop and is neither in an interrupt
> - * or NMI handler, return true.
> + * if the current CPU is not in its idle loop or is in an interrupt or
> + * NMI handler, return true.
> */
> bool notrace rcu_is_watching(void)
> {
> --
> 2.1.4
>