cpuidle: not unset the driver if it already exist
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Message ID 1570927586-12023-1-git-send-email-zhenzhong.duan@oracle.com
State Changes Requested, archived
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Series
  • cpuidle: not unset the driver if it already exist
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Commit Message

Zhenzhong Duan Oct. 13, 2019, 12:46 a.m. UTC
__cpuidle_set_driver() check if there is an already exist driver and
unset it before return with -EBUSY. The next call will succeed as it's
just unset. This is strange as we should either keep old driver and
return -EBUSY or unset and set new driver and return 0.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
---
 drivers/cpuidle/driver.c | 1 -
 1 file changed, 1 deletion(-)

Comments

Rafael J. Wysocki Oct. 22, 2019, 4:35 p.m. UTC | #1
On Mon, Oct 14, 2019 at 2:43 AM Zhenzhong Duan
<zhenzhong.duan@oracle.com> wrote:
>
> __cpuidle_set_driver() check if there is an already exist driver and
> unset it before return with -EBUSY. The next call will succeed as it's
> just unset. This is strange as we should either keep old driver and
> return -EBUSY or unset and set new driver and return 0.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> ---
>  drivers/cpuidle/driver.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index 80c1a83..a200304 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -74,7 +74,6 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
>         for_each_cpu(cpu, drv->cpumask) {
>
>                 if (__cpuidle_get_cpu_driver(cpu)) {
> -                       __cpuidle_unset_driver(drv);
>                         return -EBUSY;
>                 }

There is a bug here, but it needs to be fixed differently.

The function should check if any of the CPUs in the mask have a driver
(which is different from drv) already and if so return -EBUSY before
updating any cpuidle_drivers per-CPU pointers.

Patch
diff mbox series

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 80c1a83..a200304 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -74,7 +74,6 @@  static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 	for_each_cpu(cpu, drv->cpumask) {
 
 		if (__cpuidle_get_cpu_driver(cpu)) {
-			__cpuidle_unset_driver(drv);
 			return -EBUSY;
 		}