Hi!
The cpu_dying_mask is not only undocumented but also to some extent a
misnomer. It's purpose is to capture the last direction of a cpu_up() or
cpu_down() operation taking eventual rollback operations into account.
cpu_dying mask is not really useful for general consumption. The
cpu_dying_mask bits are sticky even after cpu_up() or cpu_down() completes.
A recent fix to plug a race in the per CPU counter code picked
cpu_dying_mask to cure it. Unfortunately this does not work as the author
probably expected and the behaviour of cpu_dying_mask is not easy to change
without breaking the only other and initial user, the scheduler.
This series addresses this by:
1) Reworking the per CPU counter hotplug mechanism so the race is fully
plugged without using cpu_dying_mask
2) Replacing the cpu_dying_mask logic with hotplug core internal state
which is exposed to the scheduler with a properly documented
function.
The series is also available from git:
git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git smp/dying_mask
Thanks
tglx
---
include/linux/cpuhotplug.h | 2 -
include/linux/cpumask.h | 21 ----------------
kernel/cpu.c | 45 +++++++++++++++++++++++++++++------
kernel/sched/core.c | 4 +--
kernel/smpboot.h | 2 +
lib/percpu_counter.c | 57 +++++++++++++++++++--------------------------
6 files changed, 67 insertions(+), 64 deletions(-)
