[PATCH v3 0/4] cpumask: Fix invalid uniprocessor assumptions

[Sander Vanheule]

On uniprocessor builds, it is currently assumed that any cpumask will
contain the single CPU: cpu0. This assumption is used to provide
optimised implementations.

The current assumption also appears to be wrong, by ignoring the fact
that users can provide empty cpumask-s. This can result in bugs as
explained in [1].

This series introduces some basic tests, and updates the optimisations
for uniprocessor builds.

[1] https://lore.kernel.org/all/20220530082552.46113-1-sander@xxxxxxxxxxxxx/

Changes since v2:
Link: https://lore.kernel.org/all/cover.1654362935.git.sander@xxxxxxxxxxxxx/
  - Put new tests after patch fixes
  - Update for_each_* macros

Changes since v1:
Link: https://lore.kernel.org/all/cover.1654201862.git.sander@xxxxxxxxxxxxx/
  - Place tests in lib/test_cpumask.c
  - Drop the modified UP code in favor of the generic SMP implementation
  - Update declaration of cpumask_next_wrap()

Sander Vanheule (4):
  cpumask: Fix invalid uniprocessor mask assumption
  lib/test: Introduce cpumask KUnit test suite
  cpumask: Add UP optimised for_each_*_cpu versions
  cpumask: Update cpumask_next_wrap() signature

 include/linux/cpumask.h |  89 +++------------------------
 lib/Kconfig.debug       |   9 +++
 lib/Makefile            |   4 +-
 lib/test_cpumask.c      | 132 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 151 insertions(+), 83 deletions(-)
 create mode 100644 lib/test_cpumask.c

-- 
2.36.1