Hi, Will, On Thu, Jul 29, 2021 at 5:55 PM Will Deacon <will@xxxxxxxxxx> wrote: > > 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 I have tried to explain in another thread. At the beginning, I thought about implementing xchg_mask for the sub-word xchg, but now I agree that atomic andnot_or is clearer and more general. Peter, what do you think? Regards, Rui
