Messages in this thread Patch in this message | | | Date | Thu, 3 Sep 2015 02:03:51 +0200 | From | Frederic Weisbecker <> | Subject | Re: Warning in irq_work_queue_on() |
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On Thu, Sep 03, 2015 at 12:24:27AM +0200, Peter Zijlstra wrote: > On Wed, Sep 02, 2015 at 11:50:22PM +0200, Frederic Weisbecker wrote: > > > > [ 875.703227] [<ffffffff810c2d74>] tick_nohz_full_kick_cpu+0x44/0x50 > > > > It happens in nohz full, but I'm not sure the guilty is nohz full. > > > > The problem here is that wake_up_nohz_cpu() selects a CPU that is offline. > > wake_up_nohz_cpu() doesn't do any such thing. Where does the selection > logic live?
Err, got confused with get_nohz_timer_target(). But yeah wake_up_nohz_cpu() is called with a CPU that is chosen by mod_timer() -> get_nohz_timer_target().
> > > But this shouldn't happen. Either it selects a CPU that is in the domain tree, > > and I suspect offline CPUs aren't supposed to be there, or it selects the current > > CPU. And if the CPU is offlined, it shouldn't be running some kthread... > > Do no assume things like that.. always check with the active mask.
Hmm, so perhaps we need something like this (makes me realize that the is_housekeeping_cpu() passes the wrong argument, no issue in practice since nohz full aren't in the domain tree but I still need to fix that along).
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0902e4d..2c10a69 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -628,7 +628,7 @@ int get_nohz_timer_target(void) rcu_read_lock(); for_each_domain(cpu, sd) { - for_each_cpu(i, sched_domain_span(sd)) { + for_each_cpu_and(i, sched_domain_span(sd), cpu_online_mask) { if (!idle_cpu(i) && is_housekeeping_cpu(cpu)) { cpu = i; goto unlock;
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