clocksource: Install completely before selecting
authorjohn stultz <johnstul@us.ibm.com>
Thu, 5 May 2011 01:16:50 +0000 (18:16 -0700)
committerThomas Gleixner <tglx@linutronix.de>
Thu, 5 May 2011 13:23:26 +0000 (15:23 +0200)
commite05b2efb82596905ebfe88e8612ee81dec9b6592
tree9b688eb473943588adf667729c0ffa3b9f032cac
parent5895198c56d131cc696556a45f7ff0ea99ac297b
clocksource: Install completely before selecting

Christian Hoffmann reported that the command line clocksource override
with acpi_pm timer fails:

 Kernel command line: <SNIP> clocksource=acpi_pm
 hpet clockevent registered
 Switching to clocksource hpet
 Override clocksource acpi_pm is not HRT compatible.
 Cannot switch while in HRT/NOHZ mode.

The watchdog code is what enables CLOCK_SOURCE_VALID_FOR_HRES, but we
actually end up selecting the clocksource before we enqueue it into
the watchdog list, so that's why we see the warning and fail to switch
to acpi_pm timer as requested. That's particularly bad when we want to
debug timekeeping related problems in early boot.

Put the selection call last.

Reported-by: Christian Hoffmann <email@christianhoffmann.info>
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: stable@kernel.org # 32...
Link: http://lkml.kernel.org/r/%3C1304558210.2943.24.camel%40work-vm%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
kernel/time/clocksource.c