search for: optimizer_hide_var

...nter being accessed. This adds an API for this and uses it in virtio. Written over the holiday and build tested only so far. This patchset is also suboptimal on e.g. x86 where e.g. smp_rmb is a nop. Sending out for early feedback/flames. Michael S. Tsirkin (4): include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR include/linux/compiler.h: allow memory operands barriers: convert a control to a data dependency virtio: use dependent_ptr_mb Documentation/memory-barriers.txt | 20 ++++++++++++++++++++ arch/alpha/include/asm/barrier.h | 1 + drivers/virtio/virtio_ring.c | 6 ++++-- include/asm-gen...

...nclude/asm-generic/barrier.h > index 2cafdbb9ae4c..fa2e2ef72b68 100644 > --- a/include/asm-generic/barrier.h > +++ b/include/asm-generic/barrier.h > @@ -70,6 +70,24 @@ > #define __smp_read_barrier_depends() read_barrier_depends() > #endif > > +#if defined(COMPILER_HAS_OPTIMIZER_HIDE_VAR) && \ > + !defined(ARCH_NEEDS_READ_BARRIER_DEPENDS) > + > +#define dependent_ptr_mb(ptr, val) ({ \ > + long dependent_ptr_mb_val = (long)(val); \ > + long dependent_ptr_mb_ptr = (long)(ptr) - dependent_ptr_mb_val; \ > + \ > + BUILD_BUG_ON(sizeof(val) >...

...nclude/asm-generic/barrier.h > index 2cafdbb9ae4c..fa2e2ef72b68 100644 > --- a/include/asm-generic/barrier.h > +++ b/include/asm-generic/barrier.h > @@ -70,6 +70,24 @@ > #define __smp_read_barrier_depends() read_barrier_depends() > #endif > > +#if defined(COMPILER_HAS_OPTIMIZER_HIDE_VAR) && \ > + !defined(ARCH_NEEDS_READ_BARRIER_DEPENDS) > + > +#define dependent_ptr_mb(ptr, val) ({ \ > + long dependent_ptr_mb_val = (long)(val); \ > + long dependent_ptr_mb_ptr = (long)(ptr) - dependent_ptr_mb_val; \ > + \ > + BUILD_BUG_ON(sizeof(val) >...

...f --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index 2cafdbb9ae4c..fa2e2ef72b68 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -70,6 +70,24 @@ #define __smp_read_barrier_depends() read_barrier_depends() #endif +#if defined(COMPILER_HAS_OPTIMIZER_HIDE_VAR) && \ + !defined(ARCH_NEEDS_READ_BARRIER_DEPENDS) + +#define dependent_ptr_mb(ptr, val) ({ \ + long dependent_ptr_mb_val = (long)(val); \ + long dependent_ptr_mb_ptr = (long)(ptr) - dependent_ptr_mb_val; \ + \ + BUILD_BUG_ON(sizeof(val) > sizeof(long)); \ + OPTIMIZER_HIDE...

...h > > index 2cafdbb9ae4c..fa2e2ef72b68 100644 > > --- a/include/asm-generic/barrier.h > > +++ b/include/asm-generic/barrier.h > > @@ -70,6 +70,24 @@ > > #define __smp_read_barrier_depends() read_barrier_depends() > > #endif > > +#if defined(COMPILER_HAS_OPTIMIZER_HIDE_VAR) && \ > > + !defined(ARCH_NEEDS_READ_BARRIER_DEPENDS) > > + > > +#define dependent_ptr_mb(ptr, val) ({ \ > > + long dependent_ptr_mb_val = (long)(val); \ > > + long dependent_ptr_mb_ptr = (long)(ptr) - dependent_ptr_mb_val; \ > > + \ > &g...

...d since it documents the kind of barrier that we are trying to use - or bad since it's more verbose and makes you choose one where they are all pretty cheap. > > Sending out for early feedback/flames. > > > > Michael S. Tsirkin (4): > > include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR > > include/linux/compiler.h: allow memory operands > > barriers: convert a control to a data dependency > > virtio: use dependent_ptr_mb > > > > Documentation/memory-barriers.txt | 20 ++++++++++++++++++++ > > arch/alpha/include/asm/barrier.h | 1 + &gt...

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