[PATCH v7 2/6] cpufreq: powernv: Hot-plug safe the kworker thread

Shilpasri G Bhat
2016-01-28T07:27:08Z

In the kworker_thread powernv_cpufreq_work_fn(), we can end up
sending an IPI to a cpu going offline. This is a rare corner case
which is fixed using {get/put}_online_cpus(). Along with this fix,
this patch adds changes to do oneshot cpumask_{clear/and} operation.

Suggested-by: Shreyas B Prabhu <shreyas@linux.vnet.ibm.com>
Suggested-by: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
No changes from v6.

Changes form v5:
- Fix the kbuild-error:
drivers/cpufreq/powernv-cpufreq.c:428:2: error: implicit declaration of
function 'get_online_cpus' [-Werror=implicit-function-declaration

drivers/cpufreq/powernv-cpufreq.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 53f980b..a271b0f 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -28,6 +28,7 @@
#include <linux/of.h>
#include <linux/reboot.h>
#include <linux/slab.h>
+#include <linux/cpu.h>

#include <asm/cputhreads.h>
#include <asm/firmware.h>
@@ -423,18 +424,19 @@ void powernv_cpufreq_work_fn(struct work_struct *work)
{
struct chip *chip = container_of(work, struct chip, throttle);
unsigned int cpu;
- cpumask_var_t mask;
+ cpumask_t mask;

- smp_call_function_any(&chip->mask,
+ get_online_cpus();
+ cpumask_and(&mask, &chip->mask, cpu_online_mask);
+ smp_call_function_any(&mask,
powernv_cpufreq_throttle_check, NULL, 0);

if (!chip->restore)
- return;
+ goto out;

chip->restore = false;
- cpumask_copy(mask, &chip->mask);
- for_each_cpu_and(cpu, mask, cpu_online_mask) {
- int index, tcpu;
+ for_each_cpu(cpu, &mask) {
+ int index;
struct cpufreq_policy policy;

cpufreq_get_policy(&policy, cpu);
@@ -442,9 +444,10 @@ void powernv_cpufreq_work_fn(struct work_struct *work)
policy.cur,
CPUFREQ_RELATION_C, &index);
powernv_cpufreq_target_index(&policy, index);
- for_each_cpu(tcpu, policy.cpus)
- cpumask_clear_cpu(tcpu, mask);
+ cpumask_andnot(&mask, &mask, policy.cpus);
}
+out:
+ put_online_cpus();
}

static char throttle_reason[][30] = {
--
1.9.3