Re: [PATCH v10 1/3] smpboot: allow excluding cpus from the smpboot threads

Don Zickus
2015-06-03T02:35:09Z

On Mon, May 04, 2015 at 06:06:24PM -0400, Chris Metcalf wrote:
> On 5/1/2015 5:23 PM, Frederic Weisbecker wrote:
> >On Fri, May 01, 2015 at 03:57:51PM -0400, Chris Metcalf wrote:
> >
> >>For example, booting with only cpu 0 as a housekeeping core (and
> >>therefore all watchdogs 1-35 on my 36-core tilegx are parked), and
> >>immediately doing "echo 0 > /proc/sys/kernel/watchdog", I see
> >>(via SysRq ^O-l) the first parked watchdog, on cpu 1, hung with:
> >>
> >> frame 0: 0xfffffff7000f2928 lock_hrtimer_base+0xb8/0xc0
> >> frame 1: 0xfffffff7000f2a28 hrtimer_try_to_cancel+0x40/0x170
> >> frame 2: 0xfffffff7000f2a28 hrtimer_try_to_cancel+0x40/0x170
> >> frame 3: 0xfffffff7000f2b98 hrtimer_cancel+0x40/0x68
> >> frame 4: 0xfffffff70014cce0 watchdog_disable+0x50/0x70
> >> frame 5: 0xfffffff70008c2d0 smpboot_thread_fn+0x350/0x438
> >> frame 6: 0xfffffff700084b28 kthread+0x160/0x178
> >Have you tried to do that before your patchset?
>
> Yes, it works fine. It requires the presence of the parked threads to trigger the issue.
>
> >>The config does not have NO_HZ_FULL_ALL or NO_HZ_FULL_SYSIDLE
> >>set, and does have RCU_FAST_NO_HZ and RCU_NOCB_CPU_ALL.
> >>
> >>I don't really know how to start debugging this, but I do know that
> >>unparking the threads first avoids the issue :-)
> >Do you have CONFIG_PROVE_LOCKING=y ?
>
> There seems to be some skew between the community version, which is throwing a
> bunch of errors when I enable PROVE_LOCKING, and our internal version where some
> things are not yet upstreamed but PROVE_LOCKING works :-)
>
> I'll try to set aside some time to reconcile the two to figure it out.

Hi Chris,

I was digging this thread back up and wondered what happened. It seems like
a v11 was going to materialize?

Cheers,
Don