Messages in this thread Patch in this message | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] smp: Do not warn if smp_call_function_single() is doing a self call. | Date | Sun, 14 Apr 2019 08:58:10 +0200 |
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Dexuan Cui <decui@microsoft.com> writes:
> If smp_call_function_single() is calling the function for itself, it's safe > to run with irqs_disabled() == true. > > I hit the warning because I'm in the below path in the .suspend callback of > a "syscore_ops" to support hibernation for a VM running on Hyper-V: > > hv_synic_cleanup() -> > clockevents_unbind_device() -> > clockevents_unbind() -> > smp_call_function_single(). >
I'd suggest fixing clockevents_unbind() instead, something like (completely untested):
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index 5e77662dd2d9..d14e881a8808 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -418,8 +418,17 @@ static void __clockevents_unbind(void *arg) static int clockevents_unbind(struct clock_event_device *ced, int cpu) { struct ce_unbind cu = { .ce = ced, .res = -ENODEV }; + int this_cpu; + + this_cpu = get_cpu(); + + if (cpu != this_cpu) + smp_call_function_single(cpu, __clockevents_unbind, &cu, 1); + else + __clockevents_unbind(&cu); + + put_cpu(); - smp_call_function_single(cpu, __clockevents_unbind, &cu, 1); return cu.res; }
> When the .suspend callback runs, only CPU0 is online and irqs_disabled() is > true. > Signed-off-by: Dexuan Cui <decui@microsoft.com> > --- > kernel/smp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index f4cf1b0bb3b8..4fdf6a378def 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -288,7 +288,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > * can't happen. > */ > WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() > - && !oops_in_progress); > + && cpu != smp_processor_id() && !oops_in_progress);
You already have 'this_cpu', no need to call smp_processor_id().
> > csd = &csd_stack; > if (!wait) {
-- Vitaly
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