On Thu, Jul 29, 2021 at 05:30:03PM +0800, Rui Wang wrote: > This patch introduce a new atomic primitive andnot_or: > > * atomic_andnot_or > * atomic_fetch_andnot_or > * atomic_fetch_andnot_or_relaxed > * atomic_fetch_andnot_or_acquire > * atomic_fetch_andnot_or_release > * atomic64_andnot_or > * atomic64_fetch_andnot_or > * atomic64_fetch_andnot_or_relaxed > * atomic64_fetch_andnot_or_acquire > * atomic64_fetch_andnot_or_release > * atomic_long_andnot_or > * atomic_long_fetch_andnot_or > * atomic_long_fetch_andnot_or_relaxed > * atomic_long_fetch_andnot_or_acquire > * atomic_long_fetch_andnot_or_release > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > Signed-off-by: Rui Wang <wangrui@xxxxxxxxxxx> > --- > include/asm-generic/atomic-instrumented.h | 72 +++++- > include/asm-generic/atomic-long.h | 62 ++++- > include/linux/atomic-arch-fallback.h | 262 +++++++++++++++++++++- > lib/atomic64_test.c | 92 ++++---- > scripts/atomic/atomics.tbl | 1 + > scripts/atomic/fallbacks/andnot_or | 25 +++ > 6 files changed, 471 insertions(+), 43 deletions(-) > create mode 100755 scripts/atomic/fallbacks/andnot_or Please see my other comments on the other patches you posted: https://lore.kernel.org/r/20210729093923.GD21151@willie-the-truck Overall, I'm not thrilled to bits by extending the atomics API with operations that cannot be implemented efficiently on any (?) architectures and are only used by the qspinlock slowpath on machines with more than 16K CPUs. I also think we're lacking documentation justifying when you would use this new primitive over e.g. a sub-word WRITE_ONCE() on architectures that support those, especially for the non-returning variants. Will
