[GIT,PULL] Please pull powerpc/linux.git powerpc-5.3-4 tag
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  • [GIT,PULL] Please pull powerpc/linux.git powerpc-5.3-4 tag
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Pull-request

https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git tags/powerpc-5.3-4

Message

Michael Ellerman Aug. 10, 2019, 10:11 a.m. UTC
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Hash: SHA256

Hi Linus,

Please pull another powerpc fix for 5.3:

The following changes since commit d7e23b887f67178c4f840781be7a6aa6aeb52ab1:

  powerpc/kasan: fix early boot failure on PPC32 (2019-07-31 22:02:52 +1000)

are available in the git repository at:

  https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git tags/powerpc-5.3-4

for you to fetch changes up to ed4289e8b48845888ee46377bd2b55884a55e60b:

  Revert "powerpc: slightly improve cache helpers" (2019-07-31 22:56:27 +1000)

- ------------------------------------------------------------------
powerpc fixes for 5.3 #4

Just one fix, a revert of a commit that was meant to be a minor improvement to
some inline asm, but ended up having no real benefit with GCC and broke booting
32-bit machines when using Clang.

Thanks to:
  Arnd Bergmann, Christophe Leroy, Nathan Chancellor, Nick Desaulniers, Segher
  Boessenkool.

- ------------------------------------------------------------------
Michael Ellerman (1):
      Revert "powerpc: slightly improve cache helpers"


 arch/powerpc/include/asm/cache.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
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Comments

Linus Torvalds Aug. 10, 2019, 5:21 p.m. UTC | #1
On Sat, Aug 10, 2019 at 3:11 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Just one fix, a revert of a commit that was meant to be a minor improvement to
> some inline asm, but ended up having no real benefit with GCC and broke booting
> 32-bit machines when using Clang.

Pulled, but whenever there are possible subtle compiler issues I get
nervous, and wonder if the problem was reported to the clang guys?

In particular, if the kernel change was technically correct, maybe
somebody else comes along in a few years and tries the same, and then
it's another odd "why doesn't this work for person X when it works
just fine for me"..

                 Linus
pr-tracker-bot@kernel.org Aug. 10, 2019, 7:30 p.m. UTC | #2
The pull request you sent on Sat, 10 Aug 2019 20:11:49 +1000:

> https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git tags/powerpc-5.3-4

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/23df57afe8eebff6ece05a815934f2f70a851e0a

Thank you!
Nathan Chancellor Aug. 10, 2019, 10:42 p.m. UTC | #3
On Sat, Aug 10, 2019 at 10:21:01AM -0700, Linus Torvalds wrote:
> On Sat, Aug 10, 2019 at 3:11 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
> >
> > Just one fix, a revert of a commit that was meant to be a minor improvement to
> > some inline asm, but ended up having no real benefit with GCC and broke booting
> > 32-bit machines when using Clang.
> 
> Pulled, but whenever there are possible subtle compiler issues I get
> nervous, and wonder if the problem was reported to the clang guys?
> 
> In particular, if the kernel change was technically correct, maybe
> somebody else comes along in a few years and tries the same, and then
> it's another odd "why doesn't this work for person X when it works
> just fine for me"..
> 
>                  Linus

It was.

https://github.com/ClangBuiltLinux/linux/issues/593

https://bugs.llvm.org/show_bug.cgi?id=42762

We're still waiting for input from the PowerPC backend maintainers as
that is most likely where this issue originates from.

Cheers,
Nathan
Michael Ellerman Aug. 10, 2019, 10:51 p.m. UTC | #4
[ expanded Cc ]

Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Sat, Aug 10, 2019 at 3:11 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
>>
>> Just one fix, a revert of a commit that was meant to be a minor improvement to
>> some inline asm, but ended up having no real benefit with GCC and broke booting
>> 32-bit machines when using Clang.
>
> Pulled, but whenever there are possible subtle compiler issues I get
> nervous, and wonder if the problem was reported to the clang guys?

Yes, sorry I should have included more context. It was actually the
Clang Linux folks who noticed it and reported it to us:
  https://github.com/ClangBuiltLinux/linux/issues/593

There's an LLVM bug filed:
  https://bugs.llvm.org/show_bug.cgi?id=42762

And I think there's now agreement that the Clang behaviour is not
correct, Nick actually sent a revert as well but I already had one
queued:
  https://patchwork.ozlabs.org/patch/1144980/

Arnd identified some work arounds, which we may end up using, but for
this cycle we thought it was preferable to just revert this change as it
didn't actually change code generation with GCC anyway.

cheers