On Tue, Jul 03, 2018 at 08:04:37AM -0700, Kevin Hilman wrote: > On Tue, Jul 3, 2018 at 3:54 AM Sudeep Holla <[email protected]> wrote: > > > > On Mon, Jul 02, 2018 at 04:44:33PM -0700, Kevin Hilman wrote: > > > Hi Sudeep, > > > > > > On Wed, May 9, 2018 at 9:02 AM Sudeep Holla <[email protected]> wrote: > > > > > > > > Checking the equality of cpumask for both new and old tick device > > > > doesn't > > > > ensure that it's CPU local device. This will cause issue if a low rating > > > > clockevent tick device is registered first followed by the registration > > > > of higher rating clockevent tick device. > > > > > > > > In such case, clockevents_released list will never get emptied as both > > > > the devices get selected as preferred one and we will loop forever in > > > > clockevents_notify_released. > > > > > > > > Cc: Frederic Weisbecker <[email protected]> > > > > Cc: Thomas Gleixner <[email protected]> > > > > Signed-off-by: Sudeep Holla <[email protected]> > > > > > > I've got a arm32 board (meson8b-odroidc1) that's been failing in > > > kernelCI.org since the merge window (boot log[1]), and I finally got > > > around to bisecting it[2]. Unfortunately, the bisect pointed at a > > > merge commit, but with some trial and error (and a suggestion by Arnd) > > > I was able to test that revering $SUBJECT commit[3], my problem goes > > > away. > > > > > > > Interesting. Sorry for causing the regression. > > > > > Another interesting data point is that disabling SMP (either by > > > "nosmp" on the command-line or CONFIG_SMP=n) also makes the problem go > > > away, without needing to revert this patch. > > > > > > > I am not sure of nosmp, but with CONFIG_SMP=n, TICK_BROADCAST also gets > > disabled. dummy_timer won't be registered I assume. > > > > I am not sure if dummy_timer is selected as it's per_cpu but the rating > > is low anyways. > > > > AFAICT, this platform, is using a single timer as a clocksource > > > ("amlogic,meson6-timer") which is not a per-CPU timer. > > > > > > > Yes that's what I could gather from DT. But this is A5 right ? It may > > have per CPU TWD(watchdof timer) but DT doesn't specify it, so should be > > fine. > > > > > I ran out of time to keep digging on this issue, and I'm still not > > > sure exactly what's going on, but I wanted to report it in case anyone > > > else has any ideas, and so we can hopefully get it fixed during the > > > -rc cycle. > > > > > > > From the log, it looks like the platform has booted to userspace. Any chance > > we can have a look at: > > $ grep "" > > /sys/devices/system/clock*/{broadcast,clock*}/{available,current}_* > > In the failing case, it doesn't boot to a shell, so I can't do that, > but after I revert the patch, I have this: >
Ah ok, does it hang when it registers clockevents ? > / # ls -l /sys/devices/system/clocksource > total 0 > drwxr-xr-x 3 root root 0 Jan 1 00:00 clocksource0 > drwxr-xr-x 2 root root 0 Jan 1 00:00 power > -rw-r--r-- 1 root root 4096 Jan 1 00:00 uevent > / # cat /sys/devices/system/clocksource/clocksource0/available_clocksource > timer jiffies Looks good. > / # cat /sys/devices/system/clocksource/clocksource0/current_clocksource > timer > OK, meson6 clocksource is active > / # cat /sys/devices/system/clockevents/broadcast/current_device > meson6_tick OK, it can support broadcast > / # cat /sys/devices/system/clockevents/clockevent0/current_device > dummy_timer > / # cat /sys/devices/system/clockevents/clockevent1/current_device > dummy_timer > / # cat /sys/devices/system/clockevents/clockevent2/current_device > dummy_timer But I can't understand why is dummy_timer the active event source and not meson6_tick. And you say this is working case ? Looks suspicious. If dummy_timer was getting used, I think meson6_tick was never utilised before as I see this platform doesn't have cpuidle(at-least from DT) -- Regards, Sudeep
