linux-toradex.git/kernel/time/clocksource.c, branch v3.15-rc8

time: Fix signedness bug in sysfs_get_uname() and its callers

2013-10-18T23:45:58+00:00

sysfs_get_uname() is erroneously declared as returning size_t even
though it may return a negative value, specifically -EINVAL.  Its
callers then check whether its return value is less than zero and indeed
that is never the case for size_t.

This patch changes sysfs_get_uname() to return ssize_t and makes sure
its callers use ssize_t accordingly.

Signed-off-by: Patrick Palka 
[jstultz: Didn't apply cleanly, as a similar partial fix was also applied
so had to resolve the collisions]
Signed-off-by: John Stultz

clocksource: Fix 'ret' data type of sysfs_override_clocksource() and sysfs_unbind_clocksource()

2013-09-17T18:19:27+00:00

sysfs_override_clocksource(): The expression 'if (ret >= 0)' is always true.
This will cause clocksource_select() to always run.
Thus modified ret to be of type ssize_t.

sysfs_unbind_clocksource(): The expression 'if (ret < 0)' is always false.
So in case sysfs_get_uname() failed, the expression won't take an effect.
Thus modified ret to be of type ssize_t.

Signed-off-by: Elad Wexler 
Signed-off-by: John Stultz

Merge branch 'fortglx/3.12/time' into fortglx/3.13/time

2013-09-17T01:54:07+00:00

Merge in the timekeeping changes that missed 3.12

Signed-off-by: John Stultz

clocksource: Extract max nsec calculation into separate function

2013-07-30T18:24:20+00:00

We need to calculate the same number in the clocksource code and
the sched_clock code, so extract this code into its own function.
We also drop the min_t and just use min() because the two types
are the same.

Signed-off-by: Stephen Boyd 
Signed-off-by: John Stultz

clocksource: Fix !CONFIG_CLOCKSOURCE_WATCHDOG compile

2013-07-22T23:00:17+00:00

If I explicitly disable the clocksource watchdog in the x86 Kconfig,
the x86 kernel will not compile unless this is properly defined.

Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: x86@kernel.org
Signed-off-by: Prarit Bhargava 
Signed-off-by: John Stultz

clocksource: Reselect clocksource when watchdog validated high-res capability

2013-07-05T09:09:28+00:00

Up to commit 5d33b883a (clocksource: Always verify highres capability)
we had no sanity check when selecting a clocksource, which prevented
that a non highres capable clocksource is used when the system already
switched to highres/nohz mode.

The new sanity check works as Alex and Tim found out. It prevents the
TSC from being used. This happens because on x86 the boot process
looks like this:

 tsc_start_freqency_validation(TSC);
 clocksource_register(HPET);
 clocksource_done_booting();
	clocksource_select()
		Selects HPET which is valid for high-res

 switch_to_highres();

 clocksource_register(TSC);
 	TSC is not selected, because it is not yet
	flagged as VALID_HIGH_RES

 clocksource_watchdog()
	Validates TSC for highres, but that does not make TSC
	the current clocksource.

Before the sanity check was added, we installed TSC unvalidated which
worked most of the time. If the TSC was really detected as unstable,
then the unstable logic removed it and installed HPET again.

The sanity check is correct and needed. So the watchdog needs to kick
a reselection of the clocksource, when it qualifies TSC as a valid
high res clocksource.

To solve this, we mark the clocksource which got the flag
CLOCK_SOURCE_VALID_FOR_HRES set by the watchdog with an new flag
CLOCK_SOURCE_RESELECT and trigger the watchdog thread. The watchdog
thread evaluates the flag and invokes clocksource_select() when set.

To avoid that the clocksource_done_booting() code, which is about to
install the first real clocksource anyway, needs to go through
clocksource_select and tick_oneshot_notify() pointlessly, split out
the clocksource_watchdog_kthread() list walk code and invoke the
select/notify only when called from clocksource_watchdog_kthread().

So clocksource_done_booting() can utilize the same splitout code
without the select/notify invocation and the clocksource_mutex
unlock/relock dance.

Reported-and-tested-by: Alex Shi 
Cc: Hans Peter Anvin 
Cc: Tim Chen 
Cc: Andi Kleen 
Tested-by: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Davidlohr Bueso 
Cc: John Stultz 
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1307042239150.11637@ionos.tec.linutronix.de
Signed-off-by: Thomas Gleixner

clocksource: Implement clocksource_select_fallback() for CONFIG_ARCH_USES_GETTIMEOFFSET=y

2013-05-28T07:48:46+00:00

commit 7eaeb34305 (clocksource: Provide unbind interface in sysfs)
implemented clocksource_select_fallback() which is not defined for
CONFIG_ARCH_USES_GETTIMEOFFSET=y. Add an empty inline function for
that.

Reported-by: Ingo Molnar 
Reported-by: fengguang.wu@intel.com
Signed-off-by: Thomas Gleixner

clockevents: Implement unbind functionality

2013-05-16T09:09:18+00:00

Provide a sysfs interface to allow unbinding of clockevent
devices. The device is unbound if it is unused or if there is a
replacement device available. Unbinding of broadcast devices is not
supported as we don't want to foster that nonsense. If no replacement
device is available the unbind returns -EBUSY. Unbind is available
from the kernel and through sysfs, which is necessary to drop the
module refcount.

Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Magnus Damm 
Link: http://lkml.kernel.org/r/20130425143436.499216659@linutronix.de
Signed-off-by: Thomas Gleixner

clocksource: Let clocksource_unregister() return success/error

2013-05-16T09:09:16+00:00

The unregister call can fail, if the clocksource is the current one
and there is no replacement clocksource available. It can also fail,
if the clocksource is the watchdog clocksource and I'm not going to
provide support for this.

Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Magnus Damm 
Link: http://lkml.kernel.org/r/20130425143436.029915527@linutronix.de
Signed-off-by: Thomas Gleixner

clocksource: Provide unbind interface in sysfs

2013-05-16T09:09:15+00:00

With the module refcount held for the current clocksource there is no
way to unload the module. 

Provide a sysfs interface which allows to unbind the clocksource. One
could argue that the clocksource override could be (ab)used to do so,
but the clocksource override cannot be used from the kernel itself,
while an unbind function can be used to programmatically check whether
a clocksource can be shutdown or not.

The unbind functionality uses the new skip current feature of
clocksource_select and verifies that a fallback clocksource has been
installed. If the clocksource which should be unbound is the current
clocksource and no fallback can be found, unbind returns -EBUSY.

This does not support the unbinding of a clocksource which is used as
the watchdog clocksource. No point in fostering crappy hardware.

Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: Magnus Damm 
Link: http://lkml.kernel.org/r/20130425143435.964218245@linutronix.de
Signed-off-by: Thomas Gleixner