[PATCH 0/3 v8] Add CPU hotplug support for PAI PMU

[Thomas Richter <tmricht@linux.ibm.com>]

V8: Add patch version 8 (v8) to each subject line

V7: Add findings from Jan Polensky
    - Fixed spelling in code and commit messages.
    - Added correct Cc: stable tag.

V6: Add findings from Sashiko
    - Remove cpus_read_lock() and cpus_read_unlock() invocations
      from CPU hotplug handlers in patch 3.

V5: Add findings from Sashiko
    - Add cpus_read_lock() and cpus_read_unlock() in patch 3.

V4: Add findings from Sumanth and updated patch 3/3.
    - Fix reference count for CPU hotplug remove while multiple
      per-task events are active.

V3: Add findings from Sumanth and updated patch 3/3.
    - Refined Fixes: commit id and messages
    - Handle cpuhp_setup_state() failure

V2: Add findings from Sumanth and updated patch 3/3.
    - handle possible NULL pointer dereference in pai_event_destroy_cpu()
    - handle possibe memory allocation failure in pai_online_cpu()
    - add Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
      to patch 1/3 and patch 2/3.

Add support for CPU hotplug add and remove for PAI PMU.

Patch 1: Change function argument list
Patch 2: Move locking from CPU scope to event scope
Patch 3: Add CPU hotplug handler

Thomas Richter (3):
  s390/pai: Use PAI PMU index as parameter replacing event
  s390/pai: Move locking to event init and delete
  s390/pai: Support CPU hotplug for PMU PAI

 arch/s390/include/asm/pai.h |   1 -
 arch/s390/kernel/perf_pai.c | 182 +++++++++++++++++++++++++-----------
 2 files changed, 128 insertions(+), 55 deletions(-)

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2.55.0