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...7 PM Will Deacon <will at kernel.org> wrote: > > In preparation for allowing architectures to define their own > implementation of the READ_ONCE() macro, move the generic > {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' > file and into a new 'rwonce.h' header under 'asm-generic'. > > Acked-by: Paul E. McKenney <paulmck at kernel.org> > Signed-off-by: Will Deacon <will at kernel.org> > --- > include/asm-generic/Kbuild | 1 + > include/asm-generic/rwonce.h | 91 ++++++++++++++++++++++++++++++++++++ &...

Now that 'smp_read_barrier_depends()' has gone the way of the Norwegian Blue, drop the inclusion of <asm/barrier.h> in 'asm-generic/rwonce.h'. This requires fixups to some architecture vdso headers which were previously relying on 'asm/barrier.h' coming in via 'linux/compiler.h'. Signed-off-by: Will Deacon <will at kernel.org> --- arch/arm/include/asm/vdso/gettimeofday.h | 1 + arch/arm64/include...

On Fri, Jul 10, 2020 at 9:52 AM Will Deacon <will at kernel.org> wrote: > > Now that 'smp_read_barrier_depends()' has gone the way of the Norwegian > Blue, drop the inclusion of <asm/barrier.h> in 'asm-generic/rwonce.h'. > > This requires fixups to some architecture vdso headers which were > previously relying on 'asm/barrier.h' coming in via 'linux/compiler.h'. > > Signed-off-by: Will Deacon <will at kernel.org> > --- > arch/arm/include/asm/vdso/gettimeofday.h...

...i, Jul 10, 2020 at 05:51:46PM +0100, Will Deacon wrote: > In preparation for allowing architectures to define their own > implementation of the READ_ONCE() macro, move the generic > {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' > file and into a new 'rwonce.h' header under 'asm-generic'. > > Acked-by: Paul E. McKenney <paulmck at kernel.org> > Signed-off-by: Will Deacon <will at kernel.org> > --- > include/asm-generic/Kbuild | 1 + > include/asm-generic/barrier.h | 2 +- > include/asm-generic/rwonce...

...at kernel.org> wrote: > > > > In preparation for allowing architectures to define their own > > implementation of the READ_ONCE() macro, move the generic > > {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' > > file and into a new 'rwonce.h' header under 'asm-generic'. > > > > Acked-by: Paul E. McKenney <paulmck at kernel.org> > > Signed-off-by: Will Deacon <will at kernel.org> > > --- > > include/asm-generic/Kbuild | 1 + > > include/asm-generic/rwonce.h | 91 ++++++++...

...yte, halfword, word and double-word accesses. Allow this to be overridden by the architecture code in the case that things like memory barriers are also required. Acked-by: Paul E. McKenney <paulmck at kernel.org> Signed-off-by: Will Deacon <will at kernel.org> --- include/asm-generic/rwonce.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h index 92cc2f223cb3..f9dfa88fc04d 100644 --- a/include/asm-generic/rwonce.h +++ b/include/asm-generic/rwonce.h @@ -33,7 +33,9 @@ * atomicity or dependency ordering guarantees. Note...

In preparation for allowing architectures to define their own implementation of the READ_ONCE() macro, move the generic {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' file and into a new 'rwonce.h' header under 'asm-generic'. Acked-by: Paul E. McKenney <paulmck at kernel.org> Signed-off-by: Will Deacon <will at kernel.org> --- include/asm-generic/Kbuild | 1 + include/asm-generic/barrier.h | 2 +- include/asm-generic/rwonce.h | 91 ++++++++++++++++++++++++++...

In preparation for allowing architectures to define their own implementation of the READ_ONCE() macro, move the generic {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' file and into a new 'rwonce.h' header under 'asm-generic'. Acked-by: Paul E. McKenney <paulmck at kernel.org> Signed-off-by: Will Deacon <will at kernel.org> --- include/asm-generic/Kbuild | 1 + include/asm-generic/rwonce.h | 91 ++++++++++++++++++++++++++++++++++++ include/linux/compiler.h...

In preparation for allowing architectures to define their own implementation of the 'READ_ONCE()' macro, move the generic '{READ,WRITE}_ONCE()' definitions out of the unwieldy 'linux/compiler.h' and into a new 'rwonce.h' header under 'asm-generic'. Signed-off-by: Will Deacon <will at kernel.org> --- include/asm-generic/Kbuild | 1 + include/asm-generic/rwonce.h | 110 +++++++++++++++++++++++++++ include/linux/compiler.h | 114 +--------------------------- include...

...n <will at kernel.org> wrote: > > In preparation for allowing architectures to define their own > implementation of the 'READ_ONCE()' macro, move the generic > '{READ,WRITE}_ONCE()' definitions out of the unwieldy 'linux/compiler.h' > and into a new 'rwonce.h' header under 'asm-generic'. Adding Christian Borntr?ger to Cc, he originally added the READ_ONCE()/WRITE_ONCE() code. I wonder if it would be appropriate now to revert back to a much simpler version of these helpers for any modern compiler. As I understand, only gcc-4.6 and gcc4.7...

...n <will at kernel.org> wrote: > > In preparation for allowing architectures to define their own > implementation of the 'READ_ONCE()' macro, move the generic > '{READ,WRITE}_ONCE()' definitions out of the unwieldy 'linux/compiler.h' > and into a new 'rwonce.h' header under 'asm-generic'. Adding Christian Borntr?ger to Cc, he originally added the READ_ONCE()/WRITE_ONCE() code. I wonder if it would be appropriate now to revert back to a much simpler version of these helpers for any modern compiler. As I understand, only gcc-4.6 and gcc4.7...

...n.org Cc: kernel-team at android.com --->8 SeongJae Park (1): Documentation/barriers/kokr: Remove references to [smp_]read_barrier_depends() Will Deacon (18): tools: bpf: Use local copy of headers including uapi/linux/filter.h compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h asm/rwonce: Allow __READ_ONCE to be overridden by the architecture alpha: Override READ_ONCE() with barriered implementation asm/rwonce: Remove smp_read_barrier_depends() invocation asm/rwonce: Don't pull <asm/barrier.h> into 'asm-generic/rwonce.h' vhost: Remove redun...

...> > >> In preparation for allowing architectures to define their own > >> implementation of the 'READ_ONCE()' macro, move the generic > >> '{READ,WRITE}_ONCE()' definitions out of the unwieldy 'linux/compiler.h' > >> and into a new 'rwonce.h' header under 'asm-generic'. > > > > Adding Christian Borntr?ger to Cc, he originally added the > > READ_ONCE()/WRITE_ONCE() > > code. > > > > I wonder if it would be appropriate now to revert back to a much simpler version > > of these helpe...

...rnd Bergmann <arnd at arndb.de> Cc: Joe Perches <joe at perches.com> Cc: Boqun Feng <boqun.feng at gmail.com> Cc: linux-alpha at vger.kernel.org Cc: virtualization at lists.linux-foundation.org --->8 Will Deacon (13): compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h READ_ONCE: Undefine internal __READ_ONCE_SIZE macro after use READ_ONCE: Allow __READ_ONCE_SIZE cases to be overridden by the architecture vhost: Remove redundant use of read_barrier_depends() barrier alpha: Override READ_ONCE() with barriered implementation READ_ONCE: Remove smp_r...

....org> wrote: >> >> In preparation for allowing architectures to define their own >> implementation of the 'READ_ONCE()' macro, move the generic >> '{READ,WRITE}_ONCE()' definitions out of the unwieldy 'linux/compiler.h' >> and into a new 'rwonce.h' header under 'asm-generic'. > > Adding Christian Borntr?ger to Cc, he originally added the > READ_ONCE()/WRITE_ONCE() > code. > > I wonder if it would be appropriate now to revert back to a much simpler version > of these helpers for any modern compiler. As I...

...n.org Cc: kernel-team at android.com --->8 SeongJae Park (1): Documentation/barriers/kokr: Remove references to [smp_]read_barrier_depends() Will Deacon (17): tools: bpf: Use local copy of headers including uapi/linux/filter.h compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h asm/rwonce: Allow __READ_ONCE to be overridden by the architecture alpha: Override READ_ONCE() with barriered implementation asm/rwonce: Remove smp_read_barrier_depends() invocation vhost: Remove redundant use of read_barrier_depends() barrier alpha: Replace smp_read_barrier_depends()...

...n.org Cc: kernel-team at android.com --->8 SeongJae Park (1): Documentation/barriers/kokr: Remove references to [smp_]read_barrier_depends() Will Deacon (17): tools: bpf: Use local copy of headers including uapi/linux/filter.h compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h asm/rwonce: Allow __READ_ONCE to be overridden by the architecture alpha: Override READ_ONCE() with barriered implementation asm/rwonce: Remove smp_read_barrier_depends() invocation vhost: Remove redundant use of read_barrier_depends() barrier alpha: Replace smp_read_barrier_depends()...

...onsequently allowing for harmful reordering by the CPU. Ensure that such transformations are harmless by overriding the generic READ_ONCE() definition with one that provides acquire semantics when building with LTO. Signed-off-by: Will Deacon <will at kernel.org> --- arch/arm64/include/asm/rwonce.h | 63 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vdso/Makefile | 2 +- arch/arm64/kernel/vdso32/Makefile | 2 +- 3 files changed, 65 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/rwonce.h diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/a...

...onsequently allowing for harmful reordering by the CPU. Ensure that such transformations are harmless by overriding the generic READ_ONCE() definition with one that provides acquire semantics when building with LTO. Signed-off-by: Will Deacon <will at kernel.org> --- arch/arm64/include/asm/rwonce.h | 63 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vdso/Makefile | 2 +- arch/arm64/kernel/vdso32/Makefile | 2 +- 3 files changed, 65 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/rwonce.h diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/a...

...READ_ONCE() in the Alpha code so that it is treated the same way as smp_load_acquire(). Acked-by: Paul E. McKenney <paulmck at kernel.org> Signed-off-by: Will Deacon <will at kernel.org> --- arch/alpha/include/asm/barrier.h | 61 ++++---------------------------- arch/alpha/include/asm/rwonce.h | 19 ++++++++++ 2 files changed, 26 insertions(+), 54 deletions(-) create mode 100644 arch/alpha/include/asm/rwonce.h diff --git a/arch/alpha/include/asm/barrier.h b/arch/alpha/include/asm/barrier.h index 92ec486a4f9e..2ecd068d91d1 100644 --- a/arch/alpha/include/asm/barrier.h +++ b/arch/alp...