On Mon, 7 Nov 2022, Greg KH wrote:
> On Thu, Oct 27, 2022 at 08:41:45AM -0400, Mikulas Patocka wrote:
> > commit d6ffe6067a54972564552ea45d320fb98db1ac5e upstream.
> >
> > Some architectures define their own arch_test_bit and they also need
> > arch_test_bit_acquire, otherwise they won't compile. We also clean up
> > the code by using the generic test_bit if that is equivalent to the
> > arch-specific version.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 8238b4579866 ("wait_on_bit: add an acquire memory barrier")
> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> >
> > ---
> > arch/alpha/include/asm/bitops.h | 7 +++++++
> > arch/h8300/include/asm/bitops.h | 3 ++-
> > arch/hexagon/include/asm/bitops.h | 15 +++++++++++++++
> > arch/ia64/include/asm/bitops.h | 7 +++++++
> > arch/m68k/include/asm/bitops.h | 6 ++++++
> > arch/s390/include/asm/bitops.h | 7 +++++++
> > arch/sh/include/asm/bitops-op32.h | 7 +++++++
> > 7 files changed, 51 insertions(+), 1 deletion(-)
>
> This is _very_ different from the upstream change that you are trying to
> backport here.
>
> Are you sure it is correct?
I compile-tested it with all the cross-compilers downloaded from
https://mirrors.edge.kernel.org/pub/tools/crosstool/ (I tried to compile
the file kernel/sched/build_utility.o that includes wait_bit.c)
> You are adding real functions for these
> arches, while the original backport was _REMOVING_ them and having the
> arch code call the generic functions.
The kernels 5.19 and older don't contain the function generic_test_bit -
and they don't contain the file
"include/asm-generic/bitops/generic-non-atomic.h" where this function is
defined. The test_bit code was refactored in 6.0 - see the commits
21bb8af513d35c005c401706030f4eb469538d1d
0e862838f290147ea9c16db852d8d494b552d38d
bb7379bfa680bd48b468e856475778db2ad866c1
e69eb9c460f128b71c6b995d75a05244e4b6cc3e
b03fc1173c0c2bb8fad61902a862985cecdc4b1b
So, the upstream patch doesn't apply to the older kernels.
> So why is this the same?
Functionally, it is equivalent if you define a function test_bit_acquire
or refer to an existing generic_test_bit_acquire that has the same
content.
Mikulas
> confused,
>
> greg k-h
>
