Messages in this thread | | | From | Leonardo Bras Soares Passos <> | Date | Thu, 3 Aug 2023 23:19:49 -0300 | Subject | Re: [RFC PATCH v2 0/3] Deduplicate RISCV cmpxchg.h and atomic.c macros |
| |
On Thu, Aug 3, 2023 at 9:53 PM Guo Ren <guoren@kernel.org> wrote: > > On Thu, Aug 3, 2023 at 1:14 PM Leonardo Bras <leobras@redhat.com> wrote: > > > > I unified previous patchsets into a single one, since the work is related. > > > > While studying riscv's cmpxchg.h file, I got really interested in > > understanding how RISCV asm implemented the different versions of > > {cmp,}xchg. > > > > When I understood the pattern, it made sense for me to remove the > > duplications and create macros to make it easier to understand what exactly > > changes between the versions: Instruction sufixes & barriers. > > > > Also, did the same kind of work on atomic.c. > > > > Note to Guo Ren: > > I did some further improvement after your previous reviews, so I ended > > up afraid including your Reviewed-by before cheching if the changes are > > ok for you. Please check it out again, I just removed some helper macros > > that were not being used elsewhere in the kernel. > I found this optimization has conflicts with the below patches: > https://lore.kernel.org/linux-riscv/20230802164701.192791-15-guoren@kernel.org/ > https://lore.kernel.org/linux-riscv/20230802164701.192791-5-guoren@kernel.org/ > > If yours merged, how do we support the inline cmpxchg/xchg_small > function?
Oh, I actually introduced my series so I could introduce new xchg and cmpxchg for size 1 and 2. Is that what your patches are about, right?
I was working on that yesterday, and decided to send the patchset without them because I was still not sure enough.
About implementation strategy, I was introducing a new macros for xchg & cmpxchg with asm which would work for both for size 1 & size 2, and use the switch-case to create the mask and and_value.
You think that works enough?
> It's very struggling to use macros to implement complex > functions.
I agree, but with this we can achieve more generic code, which makes more clear what is the pattern for given function.
> Could you consider a more relaxed optimization in which we could > insert inline cmpxchg/xchg_small?
What about this: I finish the patches I have been working with (cmpxchg & xchg for sizes 1 and 2), and if they are fine we expand this patchset with them. If not, I try relaxing them a little so we can merge with your set.
Does that work for you?
Best regards, Leo
> > > > > Thanks! > > Leo > > > > > > Changes since squashed cmpxchg: > > - Unified with atomic.c patchset > > - Rebased on top of torvalds/master (thanks Andrea Parri!) > > - Removed helper macros that were not being used elsewhere in the kernel. > > > > Changes since (cmpxchg) RFCv3: > > - Squashed the 6 original patches in 2: one for cmpxchg and one for xchg > > https://lore.kernel.org/all/20230404163741.2762165-1-leobras@redhat.com/ > > > > Changes since (cmpxchg) RFCv2: > > - Fixed macros that depend on having a local variable with a magic name > > - Previous cast to (long) is now only applied on 4-bytes cmpxchg > > https://lore.kernel.org/all/20230321074249.2221674-1-leobras@redhat.com/ > > > > Changes since (cmpxchg) RFCv1: > > - Fixed patch 4/6 suffix from 'w.aqrl' to '.w.aqrl', to avoid build error > > https://lore.kernel.org/all/20230318080059.1109286-1-leobras@redhat.com/ > > > > > > Leonardo Bras (3): > > riscv/cmpxchg: Deduplicate xchg() asm functions > > riscv/cmpxchg: Deduplicate cmpxchg() asm and macros > > riscv/atomic.h : Deduplicate arch_atomic.* > > > > arch/riscv/include/asm/atomic.h | 164 ++++++++-------- > > arch/riscv/include/asm/cmpxchg.h | 318 +++++-------------------------- > > 2 files changed, 123 insertions(+), 359 deletions(-) > > > > -- > > 2.41.0 > > > > > -- > Best Regards > Guo Ren >
| |