search for: 6601d39e8c48

So as explained in Documentation/memory-barriers.txt e.g. a load followed by a store require a full memory barrier, to avoid store being ordered before the load. Similarly load-load requires a read memory barrier. Thinking about it, we can actually create a data dependency by mixing the first loaded value into the pointer being accessed. This adds an API for this and uses it in virtio. Written

...r, val) ({ mb(); (ptr); }) So for the example of patch 4, we'd better fall back to rmb() or need a dependent_ptr_rmb()? Thanks > + > +#endif > + > #ifdef CONFIG_SMP > > #ifndef smp_mb > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 6601d39e8c48..f599c30f1b28 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -152,9 +152,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, > #endif > > #ifndef OPTIMIZER_HIDE_VAR > + > /* Make the optimizer believe the variable ca...

...r, val) ({ mb(); (ptr); }) So for the example of patch 4, we'd better fall back to rmb() or need a dependent_ptr_rmb()? Thanks > + > +#endif > + > #ifdef CONFIG_SMP > > #ifndef smp_mb > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 6601d39e8c48..f599c30f1b28 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -152,9 +152,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, > #endif > > #ifndef OPTIMIZER_HIDE_VAR > + > /* Make the optimizer believe the variable ca...

...OPTIMIZER_HIDE_VAR(dependent_ptr_mb_val); \ + (typeof(ptr))(dependent_ptr_mb_ptr + dependent_ptr_mb_val); \ +}) + +#else + +#define dependent_ptr_mb(ptr, val) ({ mb(); (ptr); }) + +#endif + #ifdef CONFIG_SMP #ifndef smp_mb diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6601d39e8c48..f599c30f1b28 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -152,9 +152,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #endif #ifndef OPTIMIZER_HIDE_VAR + /* Make the optimizer believe the variable can be manipulated arbitrarily. */ #define OP...

...endent_ptr_dma_rmb and dependent_ptr_virt_rmb. mb variant is unused right now so I'll remove it. > > > + > > +#endif > > + > > #ifdef CONFIG_SMP > > #ifndef smp_mb > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > > index 6601d39e8c48..f599c30f1b28 100644 > > --- a/include/linux/compiler.h > > +++ b/include/linux/compiler.h > > @@ -152,9 +152,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, > > #endif > > #ifndef OPTIMIZER_HIDE_VAR > > + > > /* Make the optimi...