[PATCH 0/3] nohz: Some fixes and updates

[Steven Rostedt <rostedt@goodmis.org>]

Frederic,

Can you take these patches. The first patch will need to get an
ack by one of the x86 maintainers. That one adds a new schedule_preempt_user()
that is called before going back to user space in order to safely
switch from user_context before calling schedule.

The second patch prevents LOCKUP_DETECTION from being selected if
NO_HZ_FULL is. That's because if LOCKUP_DETECTION is selected, it will
prevent NO_HZ_FULL from functioning. I first thought about having
NO_HZ_FULL depend on LOCKUP_DETECTION, but it would hide the feature.
As NO_HZ_FULL is a feature and LOCKUP_DETECTION is debugging, I
have precedence to the feature.

The last patch produces a warning if nohz_full is used or NO_HZ_FULL_ALL
is defined, and the system fails to go into nohz_full mode because
the machine's clock is unstable. We don't want users thinking they
have nohz_full but their machine can't handle it.

-- Steve

---
 arch/x86/include/asm/context_tracking.h |   10 ---------
 b/arch/x86/kernel/entry_64.S            |   26 +++++--------------------
 b/kernel/sched/core.c                   |   33 +++++++++++++++++---------------
 b/kernel/time/tick-sched.c              |    5 ++++
 b/lib/Kconfig.debug                     |    2 +
 5 files changed, 31 insertions(+), 45 deletions(-)