Commit-ID: feb245e304f343cf5e4f9123db36354144dce8a4 Gitweb: http://git.kernel.org/tip/feb245e304f343cf5e4f9123db36354144dce8a4 Author: Tejun Heo <[email protected]> AuthorDate: Thu, 16 Jun 2016 15:35:04 -0400 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 24 Jun 2016 08:26:53 +0200
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 <[email protected]> Tested-by: Gautham R. Shenoy <[email protected]> Signed-off-by: Tejun Heo <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Abdul Haleem <[email protected]> Cc: Aneesh Kumar <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4135ac8..51d7105 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)) continue; goto out; }
