linux.git/arch/s390/kernel/time.c, branch v4.13

s390/kernel: Use stop_machine_cpuslocked()

2017-05-26T08:10:41+00:00

stp_work_fn() holds get_online_cpus() while invoking stop_machine().

stop_machine() invokes get_online_cpus() as well. This is correct, but
prevents the conversion of the hotplug locking to a percpu rwsem.

Use stop_machine_cpuslocked() to avoid the nested call. Convert
*_online_cpus() to the new interfaces while at it.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner 
Acked-by: Ingo Molnar 
Acked-by: Heiko Carstens 
Cc: Paul E. McKenney 
Cc: linux-s390@vger.kernel.org
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: David Hildenbrand 
Cc: Martin Schwidefsky 
Link: http://lkml.kernel.org/r/20170524081548.250203087@linutronix.de

s390/time: Set ->min_delta_ticks and ->max_delta_ticks

2017-04-14T20:11:20+00:00

In preparation for making the clockevents core NTP correction aware,
all clockevent device drivers must set ->min_delta_ticks and
->max_delta_ticks rather than ->min_delta_ns and ->max_delta_ns: a
clockevent device's rate is going to change dynamically and thus, the
ratio of ns to ticks ceases to stay invariant.

Currently, the s390's CPU timer clockevent device is initialized as
follows:

  cd->min_delta_ns    = 1;
  cd->max_delta_ns    = LONG_MAX;

Note that the device's time to cycle conversion factor, i.e.
cd->mult / (2^cd->shift), is approx. equal to 4.

Hence, this would translate to

  cd->min_delta_ticks = 4;
  cd->max_delta_ticks = 4 * LONG_MAX;

However, a minimum value of 1ns is in the range of noise anyway and the
clockevent core will take care of this by increasing it to 1us or so.
Furthermore, 4*LONG_MAX would overflow the unsigned long argument the
clockevent devices gets programmed with.

Thus, initialize ->min_delta_ticks with 1 and ->max_delta_ticks with
ULONG_MAX.

This patch alone doesn't introduce any change in functionality as the
clockevents core still looks exclusively at the (untouched) ->min_delta_ns
and ->max_delta_ns. As soon as this has changed, a followup patch will
purge the initialization of ->min_delta_ns and ->max_delta_ns from this
driver.

Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: Daniel Lezcano 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Stephen Boyd 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Cc: David Hildenbrand 
Cc: linux-s390@vger.kernel.org
Signed-off-by: Nicolai Stange 
Signed-off-by: John Stultz

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:27+00:00

We are going to split  out of , which
will have to be picked up from other headers and .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

s390: kernel: Audit and remove any unnecessary uses of module.h

2017-02-17T06:40:31+00:00

Historically a lot of these existed because we did not have
a distinction between what was modular code and what was providing
support to modules via EXPORT_SYMBOL and friends.  That changed
when we forked out support for the latter into the export.h file.

This means we should be able to reduce the usage of module.h
in code that is obj-y Makefile or bool Kconfig.  The advantage
in doing so is that module.h itself sources about 15 other headers;
adding significantly to what we feed cpp, and it can obscure what
headers we are effectively using.

Since module.h was the source for init.h (for __init) and for
export.h (for EXPORT_SYMBOL) we consider each change instance
for the presence of either and replace as needed.  Build testing
revealed some implicit header usage that was fixed up accordingly.

Signed-off-by: Paul Gortmaker 
Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390/debug: make debug event time stamps relative to the boot TOD clock

2017-02-07T06:27:13+00:00

The debug features currently uses absolute TOD time stamps for the
debug events. Given that the TOD clock can jump forward and backward
due to STP sync checks the order of debug events can get obfuscated.

Replace the absolute TOD time stamps with a delta to the IPL time
stamp. On a STP sync check the TOD clock correction is added to
the IPL time stamp as well to make the deltas unaffected by STP
sync check.

The readout of the debug feature entries will convert the deltas
back to absolute time stamps based on the Unix epoch.

Signed-off-by: Martin Schwidefsky

s390: use false/true when using bool

2017-01-16T06:27:54+00:00

Yet another trivial patch to reduce the noise that coccinelle
generates.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

clocksource: Use a plain u64 instead of cycle_t

2016-12-25T10:04:12+00:00

There is no point in having an extra type for extra confusion. u64 is
unambiguous.

Conversion was done with the following coccinelle script:

@rem@
@@
-typedef u64 cycle_t;

@fix@
typedef cycle_t;
@@
-cycle_t
+u64

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: John Stultz

Replace with globally

2016-12-24T19:46:01+00:00

This was entirely automated, using the script by Al:

  PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*'
  sed -i -e "s!$PATT!#include !" \
        $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.

Requested-by: Al Viro 
Signed-off-by: Linus Torvalds

s390/time: fix clocksource steering for negative clock offsets

2016-11-17T05:56:38+00:00

The TOD clock offset injected by an STP sync check can be negative.
If the resulting total tod_steering_delta gets negative the kernel
will panic.

Change the type of tod_steering_delta to a signed type.

Reported-by: Dan Carpenter 
Fixes: 75c7b6f3f6ba ("s390/time: steer clocksource on STP sync events")
Signed-off-by: Martin Schwidefsky

s390/time: steer clocksource on STP sync events

2016-10-28T08:09:02+00:00

On STP sync events the TOD clock will jump in time, either forward or
backward. The TOD clocksource claims to be continuous but in case of
an STP sync with a negative offset it is not.

Subtract the offset injected by the STP sync check from the result of
the TOD clocksource to make it continuous again. Add code to drift the
offset towards zero with a fixed rate, steering 1 second in ~9 hours.

Suggested-by: David Hildenbrand 
Signed-off-by: Martin Schwidefsky