2019-10-23 05:29:46

by Zhenzhong Duan

Subject: [PATCH v2] cpuidle: not unset the driver if it already exist

__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.

check if any of the CPUs in the mask have a driver different from drv
already and if so return -EBUSY before updating any cpuidle_drivers
per-CPU pointers.

Signed-off-by: Zhenzhong Duan <[email protected]>
---
v2: update code logic per Rafael

drivers/cpuidle/driver.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 80c1a83..acfce04 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -62,24 +62,23 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
* __cpuidle_set_driver - set per CPU driver variables for the given driver.
* @drv: a valid pointer to a struct cpuidle_driver
*
- * For each CPU in the driver's cpumask, unset the registered driver per CPU
- * to @drv.
- *
- * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
+ * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
+ * different from drv already.
*/
static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
{
int cpu;

for_each_cpu(cpu, drv->cpumask) {
+ struct cpuidle_driver *old_drv;

- if (__cpuidle_get_cpu_driver(cpu)) {
- __cpuidle_unset_driver(drv);
+ old_drv = __cpuidle_get_cpu_driver(cpu);
+ if (old_drv && old_drv != drv)
return -EBUSY;
- }
+ }

+ for_each_cpu(cpu, drv->cpumask)
per_cpu(cpuidle_drivers, cpu) = drv;
- }

return 0;
}
--
1.8.3.1

2019-10-28 21:09:33

by Rafael J. Wysocki

Subject: Re: [PATCH v2] cpuidle: not unset the driver if it already exist

On Wednesday, October 23, 2019 3:57:14 AM CET Zhenzhong Duan 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.
>
> check if any of the CPUs in the mask have a driver different from drv
> already and if so return -EBUSY before updating any cpuidle_drivers
> per-CPU pointers.
>
> Signed-off-by: Zhenzhong Duan <[email protected]>
> ---
> v2: update code logic per Rafael
>
> drivers/cpuidle/driver.c | 15 +++++++--------
> 1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index 80c1a83..acfce04 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -62,24 +62,23 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
> * __cpuidle_set_driver - set per CPU driver variables for the given driver.
> * @drv: a valid pointer to a struct cpuidle_driver
> *
> - * For each CPU in the driver's cpumask, unset the registered driver per CPU
> - * to @drv.
> - *
> - * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
> + * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
> + * different from drv already.
> */
> static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
> {
> int cpu;
>
> for_each_cpu(cpu, drv->cpumask) {
> + struct cpuidle_driver *old_drv;
>
> - if (__cpuidle_get_cpu_driver(cpu)) {
> - __cpuidle_unset_driver(drv);
> + old_drv = __cpuidle_get_cpu_driver(cpu);
> + if (old_drv && old_drv != drv)
> return -EBUSY;
> - }
> + }
>
> + for_each_cpu(cpu, drv->cpumask)
> per_cpu(cpuidle_drivers, cpu) = drv;
> - }
>
> return 0;
> }
>

Applied as 5.5 material, thanks!