Subject: Re: linux-next: Tree for Feb 8 [ smp|cpufreq: WARNING: at kernel/smp.c:245 smp_call_function_single ]

From: Ingo Molnar <[email-masked]>
Date: Fri, 8 Feb 2013 14:58:01 +0100

* Rafael J. Wysocki <[email-masked]> wrote:

> On Friday, February 08, 2013 01:47:44 PM Sedat Dilek wrote:
> > On Fri, Feb 8, 2013 at 12:53 PM, Hillf Danton <[email-masked]> wrote:
> > > Hello Sedat
> > >
> > > On Fri, Feb 8, 2013 at 4:46 PM, Sedat Dilek <[email-masked]> wrote:
> > >> On Fri, Feb 8, 2013 at 5:31 AM, Stephen Rothwell <[email-masked]> wrote:
> > >> With today's Linux-Next I see this warning:
> > >>
> > >> [    0.377442] ------------[ cut here ]------------
> > >> [    0.377452] WARNING: at kernel/smp.c:245
> > >> smp_call_function_single+0x146/0x190()
> > >> [    0.377455] Hardware name: 530U3BI/530U4BI/530U4BH
> > >> [    0.377458] Modules linked in:
> > >> [    0.377463] Pid: 1, comm: swapper/0 Not tainted
> > >> 3.8.0-rc6-next20130208-1-iniza-small #1
> > >> [    0.377467] Call Trace:
> > >> [    0.377473]  [<ffffffff8105a5ef>] warn_slowpath_common+0x7f/0xc0
> > >> [    0.377479]  [<ffffffff81579130>] ? acpi_cpufreq_target+0x2c0/0x2c0
> > >> [    0.377483]  [<ffffffff8105a64a>] warn_slowpath_null+0x1a/0x20
> > >> [    0.377487]  [<ffffffff810bb7e6>] smp_call_function_single+0x146/0x190
> > >> [    0.377492]  [<ffffffff81579130>] ? acpi_cpufreq_target+0x2c0/0x2c0
> > >> [    0.377496]  [<ffffffff810bb881>] smp_call_function_any+0x51/0x100
> > >> [    0.377500]  [<ffffffff815788c9>] get_cur_val+0x99/0x130
> > >> [    0.377504]  [<ffffffff81579444>] ? acpi_cpufreq_cpu_init+0x2b4/0x6a0
> > >> [    0.377508]  [<ffffffff81578db0>] get_cur_freq_on_cpu+0x60/0x80
> > >> [    0.377512]  [<ffffffff815795a2>] acpi_cpufreq_cpu_init+0x412/0x6a0
> > >> [    0.377517]  [<ffffffff81575bb9>] cpufreq_add_dev+0x2d9/0x4f0
> > >> [    0.377523]  [<ffffffff81d44b22>] ? cpufreq_gov_dbs_init+0x2c/0x2c
> > >> [    0.377528]  [<ffffffff8145d379>] subsys_interface_register+0x89/0xd0
> > >> [    0.377533]  [<ffffffff81573dee>] cpufreq_register_driver+0x8e/0x180
> > >> [    0.377537]  [<ffffffff81d44c18>] acpi_cpufreq_init+0xf6/0x1f8
> > >> [    0.377542]  [<ffffffff814608e6>] ? platform_driver_register+0x46/0x50
> > >> [    0.377547]  [<ffffffff8100206f>] do_one_initcall+0x3f/0x170
> > >> [    0.377553]  [<ffffffff81d07029>] kernel_init_freeable+0x13e/0x1cd
> > >> [    0.377560]  [<ffffffff81d06895>] ? do_early_param+0x86/0x86
> > >> [    0.377565]  [<ffffffff8169cf20>] ? rest_init+0x80/0x80
> > >> [    0.377569]  [<ffffffff8169cf2e>] kernel_init+0xe/0xf0
> > >> [    0.377575]  [<ffffffff816c722c>] ret_from_fork+0x7c/0xb0
> > >> [    0.377578]  [<ffffffff8169cf20>] ? rest_init+0x80/0x80
> > >> [    0.377581] ---[ end trace c6ec8280ce20313a ]---
> > >>
> > >> kernel/smp.c: Line #245 see [1].
> > >>
> > > Can you please try the following?
> > >
> > > --- a/kernel/smp.c      Fri Feb  8 19:25:32 2013
> > > +++ b/kernel/smp.c      Fri Feb  8 19:53:14 2013
> > > @@ -241,7 +241,7 @@ int smp_call_function_single(int cpu, sm
> > >          * send smp call function interrupt to this cpu and as such deadlocks
> > >          * can't happen.
> > >          */
> > > -       WARN_ON_ONCE(cpu_online(this_cpu) && (irqs_disabled() || in_interrupt())
> > > +       WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
> > >                      && !oops_in_progress);
> > >
> > >         if (cpu == this_cpu) {
> > > --
> > 
> > NO, it doesn't.
> > 
> > So, you want to partly revert...
> > 
> > commit b29f39c7c3e75a741a7da88244ec707f293ec04c
> > "smp: Give WARN()ing if in_interrupt() when calling
> > smp_call_function_many()/single()"
> > 
> > ...why not completely?
> > 
> > This patch was in last days Linux-Next and did not cause troubles (AFAICS).
> 
> This problem was introduced by some cpufreq changes that have 
> been dropped from linux-next for now (they are still present 
> in the one you're testing, though).

SMP cross-calls from IRQ context are generally unsafe, so I'd 
suggest a good look at the cpufreq changes first, before 
reverting the stronger debugging we introduced.

Thanks,

	Ingo