[PATCH 0/2] timekeeping: Fix change_clocksource() for PM and sh_cmt

From: Niklas Söderlund
Date: Fri Dec 04 2020 - 21:27:44 EST

Next message: Niklas Söderlund: "[PATCH 2/2] timekeeping: Allow runtime PM from change_clocksource()"
Previous message: Jakub Kicinski: "Re: [PATCH net-next 2/3] net: hns3: add priv flags support to switch limit promisc mode"
Next in thread: Niklas Söderlund: "[PATCH 2/2] timekeeping: Allow runtime PM from change_clocksource()"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hello,

This series is an attempt to fix two potential deadlock situations and
allowing the tools/testing/selftests/timers/clocksource-switch test to
pass for the sh_cmt driver.

The two patches are not directly related, but patch 1/2 fixes a local
problem in the sh_cmt driver that hides the issue in the timekeeping
core addressed in patch 2/2. In trying to give as an complete view of my
problem so I have opted to keep the two patches together.

I'm in no way an expert on the timekeeping core but with these two
patches applied I can pass the clocksource-switch selftest on R-Car Gen2
and Gen3 boards. The selftest rapidly switches clock sources and without
these patches I lockup somewhere and the test fails, with this applied
it passes. Please se end of cover-letter for logs of the selftest runs,
and each patch for possible deadlock information.

For each patch the easiest way demonstrate the each of the deadlock
situations all that is needed is to select the CMT clocksource,

# echo e60f0000.timer > /sys/devices/system/clocksource/clocksource0/current_clocksource

I have tested on-top of v5.10-rc6 on R-Car M3-N (CMT0 and CMT1) and
Koelsch (CMT0).

* R-Car M3-N without this series applied

# ./clocksource-switch
Validating clocksource arch_sys_counter
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Validating clocksource e60f0000.timer
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Validating clocksource e6130000.timer
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Running Asynchronous Switching Tests...
Consistent CLOCK_REALTIME Sat Dec 5 01:52:28 2020

1607133200:750182652
1607133200:750182652
1607133200:750182772
1607133200:750182892
1607133200:750182892
1607133200:750183012
1607133200:750183133
1607133200:750183133
1607133200:750183253
1607133200:750183373
1607133200:750183373
1607133200:750183493
1607133200:750183493
1607133200:750183613
1607133200:750183734
1607133200:750183734
1607133200:750183854
1607133200:750183974
1607133200:750183974
1607133200:750184094
1607133200:750184214
1607133200:750184214
1607133200:750184335
1607133200:750184455
1607133200:750184455
1607133200:750184575
1607133200:750184695
1607133200:750184695
1607133200:750184815
1607133200:750184936
1607133200:750184936
1607133200:750185056
1607133200:750185056
1607133200:750185176
1607133200:750185296
1607133200:750185296
1607133200:750185416
1607133200:750185536
1607133200:750185536
1607133200:750185657
1607133200:750185777
1607133200:750185777
1607133200:750185897
1607133200:750186017
1607133200:750295633
1607133200:750295633
1607133200:750541817
1607133200:750541817
1607133200:750541817
1607133200:750541817
1607133200:750541817
1607133200:750541817
1607133200:750541817
--------------------
1607133200:750541817
1607133200:750295633
--------------------
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
1607133200:750295633
Delta: 246184 ns
Sat Dec 5 01:53:20 2020

[FAILED]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0

* R-Car M3-N with this series applied

# ./clocksource-switch
Validating clocksource arch_sys_counter
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Validating clocksource e60f0000.timer
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Validating clocksource e6130000.timer
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Running Asynchronous Switching Tests...
Consistent CLOCK_REALTIME [OK]
Consistent CLOCK_MONOTONIC [OK]
Consistent CLOCK_PROCESS_CPUTIME_ID [OK]
Consistent CLOCK_THREAD_CPUTIME_ID [OK]
Consistent CLOCK_MONOTONIC_RAW [OK]
Consistent CLOCK_REALTIME_COARSE [OK]
Consistent CLOCK_MONOTONIC_COARSE [OK]
Consistent CLOCK_BOOTTIME [OK]
Consistent CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
Nanosleep CLOCK_REALTIME [OK]
Nanosleep CLOCK_MONOTONIC [OK]
Nanosleep CLOCK_MONOTONIC_RAW [UNSUPPORTED]
Nanosleep CLOCK_REALTIME_COARSE [UNSUPPORTED]
Nanosleep CLOCK_MONOTONIC_COARSE [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME [OK]
Nanosleep CLOCK_REALTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_BOOTTIME_ALARM [UNSUPPORTED]
Nanosleep CLOCK_TAI [OK]
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0

Niklas Söderlund (2):
clocksource/drivers/sh_cmt: Fix potential deadlock when calling
runtime PM
timekeeping: Allow runtime PM from change_clocksource()

drivers/clocksource/sh_cmt.c | 18 ++++++++++++++----
kernel/time/timekeeping.c | 36 +++++++++++++++++++++++-------------
2 files changed, 37 insertions(+), 17 deletions(-)

--
2.29.2

Next message: Niklas Söderlund: "[PATCH 2/2] timekeeping: Allow runtime PM from change_clocksource()"
Previous message: Jakub Kicinski: "Re: [PATCH net-next 2/3] net: hns3: add priv flags support to switch limit promisc mode"
Next in thread: Niklas Söderlund: "[PATCH 2/2] timekeeping: Allow runtime PM from change_clocksource()"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]