path: root/kernel
diff options
authorTejun Heo <>2016-06-16 15:35:04 -0400
committerIngo Molnar <>2016-06-24 08:26:53 +0200
commitfeb245e304f343cf5e4f9123db36354144dce8a4 (patch)
treec36f1ab5cde6031e21c4da6a74cb9b63159b62ef /kernel
parent754bd598be9bbc953bc709a9e8ed7f3188bfb9d7 (diff)
sched/core: Allow kthreads to fall back to online && !active cpus
During CPU hotplug, CPU_ONLINE callbacks are run while the CPU is online but not active. A CPU_ONLINE callback may create or bind a kthread so that its cpus_allowed mask only allows the CPU which is being brought online. The kthread may start executing before the CPU is made active and can end up in select_fallback_rq(). In such cases, the expected behavior is selecting the CPU which is coming online; however, because select_fallback_rq() only chooses from active CPUs, it determines that the task doesn't have any viable CPU in its allowed mask and ends up overriding it to cpu_possible_mask. CPU_ONLINE callbacks should be able to put kthreads on the CPU which is coming online. Update select_fallback_rq() so that it follows cpu_online() rather than cpu_active() for kthreads. Reported-by: Gautham R Shenoy <> Tested-by: Gautham R. Shenoy <> Signed-off-by: Tejun Heo <> Signed-off-by: Peter Zijlstra (Intel) <> Cc: Abdul Haleem <> Cc: Aneesh Kumar <> Cc: Linus Torvalds <> Cc: Michael Ellerman <> Cc: Peter Zijlstra <> Cc: Thomas Gleixner <> Cc: Cc: Link: Signed-off-by: Ingo Molnar <>
Diffstat (limited to 'kernel')
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4135ac83cb65..51d7105f529a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1536,7 +1536,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
for (;;) {
/* Any allowed, online CPU? */
for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
- if (!cpu_active(dest_cpu))
+ if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu))
+ continue;
+ if (!cpu_online(dest_cpu))
goto out;