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Subject[PATCH 4/4] CPU hotplug, cpusets: Differentiate the CPU online and CPU offline callbacks
Date
Call scan_cpusets_during_cpu_online() upon CPU online events and
call scan_for_empty_cpusets() upon CPU offline events.

Reported-by: Prashanth K. Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
---

include/linux/cpuset.h | 4 ++--
kernel/cpuset.c | 9 +++++++--
kernel/sched/core.c | 12 ++++++++++--
3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index e9eaec5..acfe484 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -20,7 +20,7 @@ extern int number_of_cpusets; /* How many cpusets are defined in system? */

extern int cpuset_init(void);
extern void cpuset_init_smp(void);
-extern void cpuset_update_active_cpus(void);
+extern void cpuset_update_active_cpus(bool cpu_online);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern int cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -133,7 +133,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}

-static inline void cpuset_update_active_cpus(void)
+static inline void cpuset_update_active_cpus(bool cpu_online)
{
partition_sched_domains(1, NULL, NULL);
}
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c56e705..d863df5 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2223,8 +2223,10 @@ static void scan_for_empty_cpusets(struct cpuset *root)
*
* Called within get_online_cpus(). Needs to call cgroup_lock()
* before calling generate_sched_domains().
+ *
+ * @cpu_online: whether this is a CPU online event or a CPU offline event.
*/
-void cpuset_update_active_cpus(void)
+void cpuset_update_active_cpus(bool cpu_online)
{
struct sched_domain_attr *attr;
cpumask_var_t *doms;
@@ -2234,7 +2236,10 @@ void cpuset_update_active_cpus(void)
mutex_lock(&callback_mutex);
cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
mutex_unlock(&callback_mutex);
- scan_for_empty_cpusets(&top_cpuset);
+ if (cpu_online)
+ scan_cpusets_during_cpu_online(&top_cpuset);
+ else
+ scan_for_empty_cpusets(&top_cpuset);
ndoms = generate_sched_domains(&doms, &attr);
cgroup_unlock();

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5255c9d..d4dd9ef 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6732,7 +6732,11 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
- cpuset_update_active_cpus();
+ /*
+ * The 'true' value indicates that we are calling the function
+ * due to a CPU online operation in progress.
+ */
+ cpuset_update_active_cpus(true);
return NOTIFY_OK;
default:
return NOTIFY_DONE;
@@ -6744,7 +6748,11 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
- cpuset_update_active_cpus();
+ /*
+ * The 'false' value indicates that we are calling the function
+ * due to a CPU offline operation in progress.
+ */
+ cpuset_update_active_cpus(false);
return NOTIFY_OK;
default:
return NOTIFY_DONE;


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