Mark Rutland <mark.rutl...@arm.com> writes: > For several reasons, it is desirable to use {READ,WRITE}_ONCE() in > preference to ACCESS_ONCE(), and new code is expected to use one of the > former. So far, there's been no reason to change most existing uses of > ACCESS_ONCE(), as these aren't currently harmful. > > However, for some features it is necessary to instrument reads and > writes separately, which is not possible with ACCESS_ONCE(). This > distinction is critical to correct operation. > > The bulk of the kernel code can be transformed via Coccinelle to use > {READ,WRITE}_ONCE(), though this only modifies users of ACCESS_ONCE(), > and not the implementation itself. As such, it has the potential to > break homebrew ACCESS_ONCE() macros seen in some user code in the kernel > tree (e.g. the virtio code, as fixed in commit ea9156fb3b71d9f7). > > To avoid fragility if/when that transformation occurs, and to align with > the preferred usage of {READ,WRITE}_ONCE(), this patch updates the DSCR > selftest code to use READ_ONCE() rather than ACCESS_ONCE(). There should > be no functional change as a result of this patch. > > Signed-off-by: Mark Rutland <mark.rutl...@arm.com> > Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Cc: Michael Ellerman <m...@ellerman.id.au> > Cc: Paul Mackerras <pau...@samba.org> > Cc: Shuah Khan <sh...@kernel.org> > --- > tools/testing/selftests/powerpc/dscr/dscr.h | 2 +- > tools/testing/selftests/powerpc/dscr/dscr_default_test.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-)
Acked-by: Michael Ellerman <m...@ellerman.id.au> cheers