Messages in this thread Patch in this message | | | Date | Fri, 10 Apr 2009 09:21:08 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] unbreak alpha percpu |
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Hmm. I certainly personally _much_ prefer this version.
It looks like this actually simplifies things for S390 too (no more simple_identifier_##var games), and generally just looks better. And seeing that the S390 special case is no longer S390-specific is also a good sign, imho.
Sorry for including the whole message, but I'm adding s390 and percpu people to the cc. Guys - original uncorrupted patch on lkml.
Linus
--- On Fri, 10 Apr 2009, Al Viro wrote: > On Fri, Apr 10, 2009 at 04:12:24PM +0100, Al Viro wrote: > > asm-generic/percpu.h is *NOT* included by every asm/percpu.h out there. > > Namely, alpha can't use it since it needs the var name in > > SHIFT_PERCPU_PTR - &per_cpu_var(var) won't do at all. So adding stuff > > to asm-generic/percpu.h and expecting it to be picked by everything > > is not going to work. > > > > Frankly, I'd rather have SHIFT_PERCPU_PTR() calling conventions changed, > > but for now the patch below will do. > > > > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> > > Alternative patch (changing SHIFT_PERCPU_PTR() arguments and switching > alpha to asm-generic/percpu.h) would be this (only build-tested, though): > > diff --git a/arch/alpha/include/asm/percpu.h b/arch/alpha/include/asm/percpu.h > index 3495e8e..1c52a2d 100644 > --- a/arch/alpha/include/asm/percpu.h > +++ b/arch/alpha/include/asm/percpu.h > @@ -3,33 +3,8 @@ > #include <linux/compiler.h> > #include <linux/threads.h> > > -/* > - * Determine the real variable name from the name visible in the > - * kernel sources. > - */ > -#define per_cpu_var(var) per_cpu__##var > - > #ifdef CONFIG_SMP > - > -/* > - * per_cpu_offset() is the offset that has to be added to a > - * percpu variable to get to the instance for a certain processor. > - */ > -extern unsigned long __per_cpu_offset[NR_CPUS]; > - > -#define per_cpu_offset(x) (__per_cpu_offset[x]) > - > -#define __my_cpu_offset per_cpu_offset(raw_smp_processor_id()) > -#ifdef CONFIG_DEBUG_PREEMPT > -#define my_cpu_offset per_cpu_offset(smp_processor_id()) > -#else > -#define my_cpu_offset __my_cpu_offset > -#endif > - > -#ifndef MODULE > -#define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset)) > -#define PER_CPU_ATTRIBUTES > -#else > +#ifdef MODULE > /* > * To calculate addresses of locally defined variables, GCC uses 32-bit > * displacement from the GP. Which doesn't work for per cpu variables in > @@ -39,40 +14,15 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; > * ldq instruction with a 'literal' relocation. > */ > #define SHIFT_PERCPU_PTR(var, offset) ({ \ > - extern int simple_identifier_##var(void); \ > unsigned long __ptr, tmp_gp; \ > asm ( "br %1, 1f \n\ > 1: ldgp %1, 0(%1) \n\ > ldq %0, per_cpu__" #var"(%1)\t!literal" \ > : "=&r"(__ptr), "=&r"(tmp_gp)); \ > (typeof(&per_cpu_var(var)))(__ptr + (offset)); }) > - > -#define PER_CPU_ATTRIBUTES __used > - > #endif /* MODULE */ > - > -/* > - * A percpu variable may point to a discarded regions. The following are > - * established ways to produce a usable pointer from the percpu variable > - * offset. > - */ > -#define per_cpu(var, cpu) \ > - (*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu))) > -#define __get_cpu_var(var) \ > - (*SHIFT_PERCPU_PTR(var, my_cpu_offset)) > -#define __raw_get_cpu_var(var) \ > - (*SHIFT_PERCPU_PTR(var, __my_cpu_offset)) > - > -#else /* ! SMP */ > - > -#define per_cpu(var, cpu) (*((void)(cpu), &per_cpu_var(var))) > -#define __get_cpu_var(var) per_cpu_var(var) > -#define __raw_get_cpu_var(var) per_cpu_var(var) > - > -#define PER_CPU_ATTRIBUTES > - > #endif /* SMP */ > > -#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu_var(name) > +#include <asm-generic/percpu.h> > > #endif /* __ALPHA_PERCPU_H */ > diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h > index 408d60b..6a71d73 100644 > --- a/arch/s390/include/asm/percpu.h > +++ b/arch/s390/include/asm/percpu.h > @@ -13,20 +13,18 @@ > */ > #if defined(__s390x__) && defined(MODULE) > > -#define SHIFT_PERCPU_PTR(ptr,offset) (({ \ > - extern int simple_identifier_##var(void); \ > +#define SHIFT_PERCPU_PTR(var,offset) (({ \ > unsigned long *__ptr; \ > asm ( "larl %0, %1@GOTENT" \ > - : "=a" (__ptr) : "X" (ptr) ); \ > - (typeof(ptr))((*__ptr) + (offset)); })) > + : "=a" (__ptr) : "X" (&per_cpu_var(var)) ); \ > + (typeof(&per_cpu_var(var)))((*__ptr) + (offset)); })) > > #else > > -#define SHIFT_PERCPU_PTR(ptr, offset) (({ \ > - extern int simple_identifier_##var(void); \ > +#define SHIFT_PERCPU_PTR(var, offset) (({ \ > unsigned long __ptr; \ > - asm ( "" : "=a" (__ptr) : "0" (ptr) ); \ > - (typeof(ptr)) (__ptr + (offset)); })) > + asm ( "" : "=a" (__ptr) : "0" (&per_cpu_var(var)) ); \ > + (typeof(&per_cpu_var(var))) (__ptr + (offset)); })) > > #endif > > diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h > index 00f45ff..7463700 100644 > --- a/include/asm-generic/percpu.h > +++ b/include/asm-generic/percpu.h > @@ -42,10 +42,10 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; > /* > * Add a offset to a pointer but keep the pointer as is. > * > - * Only S390 provides its own means of moving the pointer. > + * Only S390 and Alpha provide their own means of moving the pointer. > */ > #ifndef SHIFT_PERCPU_PTR > -#define SHIFT_PERCPU_PTR(__p, __offset) RELOC_HIDE((__p), (__offset)) > +#define SHIFT_PERCPU_PTR(__v, __offset) RELOC_HIDE(&per_cpu_var(__v), (__offset)) > #endif > > /* > @@ -54,11 +54,11 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; > * offset. > */ > #define per_cpu(var, cpu) \ > - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu))) > + (*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu))) > #define __get_cpu_var(var) \ > - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), my_cpu_offset)) > + (*SHIFT_PERCPU_PTR(var, my_cpu_offset)) > #define __raw_get_cpu_var(var) \ > - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), __my_cpu_offset)) > + (*SHIFT_PERCPU_PTR(var, __my_cpu_offset)) > > > #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA >
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