[PATCH 5.4 104/177] cpuidle: Do not unset the driver if it is there already

Greg Kroah-Hartman
2019-12-16T18:18:42Z

From: Zhenzhong Duan <zhenzhong.duan@oracle.com>

commit 918c1fe9fbbe46fcf56837ff21f0ef96424e8b29 upstream.

Fix __cpuidle_set_driver() to check if any of the CPUs in the mask has
a driver different from drv already and, if so, return -EBUSY before
updating any cpuidle_drivers per-CPU pointers.

Fixes: 82467a5a885d ("cpuidle: simplify multiple driver support")
Cc: 3.11+ <stable@vger.kernel.org> # 3.11+
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -62,24 +62,23 @@ static inline void __cpuidle_unset_drive
* __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;
}