| Message ID | 20230531132323.722039569@infradead.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() | expand |
On Wed, May 31, 2023, at 15:08, Peter Zijlstra wrote: > Some 64bit architectures do not advertise __SIZEOF_INT128__ on all > supported compiler versions. Notably the HPPA64 only started doing > with GCC-11. I checked the other compilers to be sure that anything else we support (gcc-5.1 and up) across all 64-bit architectures does support int128. It would be nice to have the hack more localized to parisc and guarded with a CONFIG_GCC_VERSION check so we can kill it off in the future, once we drop either gcc-10 or parisc support. > +#ifndef __SIZEOF_INT128__ > +#define raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval) \ > +({ \ > + typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \ > + typeof(pcp) __val = *__p, __old = *(ovalp); \ > + bool __ret; \ > + if (!__builtin_memcmp(&__val, &__old, sizeof(pcp))) { \ > + *__p = nval; \ > + __ret = true; \ > + } else { \ > + *(ovalp) = __val; \ > + __ret = false; \ > + } \ > + __ret; \ > +}) > + > +#define raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval) \ > +({ \ > + typeof(pcp) __old = (oval); \ > + raw_cpu_generic_try_cmpxchg_memcpy(pcp, &__old, nval); \ > + __old; \ > +}) Instead of having this in include/asm-generic under !__SIZEOF_INT128__, could you just move this into the parisc files with a compiler version check? Arnd
On Wed, May 31, 2023 at 04:21:22PM +0200, Arnd Bergmann wrote: > On Wed, May 31, 2023, at 15:08, Peter Zijlstra wrote: > > Some 64bit architectures do not advertise __SIZEOF_INT128__ on all > > supported compiler versions. Notably the HPPA64 only started doing > > with GCC-11. > > I checked the other compilers to be sure that anything else > we support (gcc-5.1 and up) across all 64-bit architectures > does support int128. Oh excellent -- I didn't have sufficient old cross compilers to verify, hence me not doing what you suggest below. If HPPA64 really is the only one so affected, then yes, I can move this hack into arch/parisc.
--- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -313,6 +313,35 @@ do { \ #define raw_cpu_xchg_8(pcp, nval) raw_cpu_generic_xchg(pcp, nval) #endif +#ifndef __SIZEOF_INT128__ +#define raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval) \ +({ \ + typeof(pcp) *__p = raw_cpu_ptr(&(pcp)); \ + typeof(pcp) __val = *__p, __old = *(ovalp); \ + bool __ret; \ + if (!__builtin_memcmp(&__val, &__old, sizeof(pcp))) { \ + *__p = nval; \ + __ret = true; \ + } else { \ + *(ovalp) = __val; \ + __ret = false; \ + } \ + __ret; \ +}) + +#define raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval) \ +({ \ + typeof(pcp) __old = (oval); \ + raw_cpu_generic_try_cmpxchg_memcpy(pcp, &__old, nval); \ + __old; \ +}) + +#define raw_cpu_cmpxchg128(pcp, oval, nval) \ + raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval) +#define raw_cpu_try_cmpxchg128(pcp, ovalp, nval) \ + raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval) +#endif + #ifndef raw_cpu_try_cmpxchg_1 #ifdef raw_cpu_cmpxchg_1 #define raw_cpu_try_cmpxchg_1(pcp, ovalp, nval) \ @@ -503,6 +532,33 @@ do { \ #define this_cpu_xchg_8(pcp, nval) this_cpu_generic_xchg(pcp, nval) #endif +#ifndef __SIZEOF_INT128__ +#define this_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval) \ +({ \ + bool __ret; \ + unsigned long __flags; \ + raw_local_irq_save(__flags); \ + __ret = raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval); \ + raw_local_irq_restore(__flags); \ + __ret; \ +}) + +#define this_cpu_generic_cmpxchg_memcmp(pcp, oval, nval) \ +({ \ + typeof(pcp) __ret; \ + unsigned long __flags; \ + raw_local_irq_save(__flags); \ + __ret = raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval); \ + raw_local_irq_restore(__flags); \ + __ret; \ +}) + +#define this_cpu_cmpxchg128(pcp, oval, nval) \ + this_cpu_generic_cmpxchg_memcmp(pcp, oval, nval) +#define this_cpu_try_cmpxchg128(pcp, ovalp, nval) \ + this_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval) +#endif + #ifndef this_cpu_try_cmpxchg_1 #ifdef this_cpu_cmpxchg_1 #define this_cpu_try_cmpxchg_1(pcp, ovalp, nval) \ --- a/include/linux/types.h +++ b/include/linux/types.h @@ -13,6 +13,13 @@ #ifdef __SIZEOF_INT128__ typedef __s128 s128; typedef __u128 u128; +#else +#ifdef CONFIG_64BIT +/* hack for this_cpu_cmpxchg128 */ +typedef struct { + u64 a, b; +} u128 __attribute__((aligned(16))); +#endif #endif typedef u32 __kernel_dev_t;
Some 64bit architectures do not advertise __SIZEOF_INT128__ on all supported compiler versions. Notably the HPPA64 only started doing with GCC-11. Since the per-cpu ops are universally availably, and this_cpu_{,try_}cmpxchg128() is expected to be available on all 64bit architectures a wee bodge is in order. Sadly, while C reverts to memcpy() for assignment of POD types, it does not revert to memcmp() for for equality. Therefore frob that manually. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- include/asm-generic/percpu.h | 56 +++++++++++++++++++++++++++++++++++++++++++ include/linux/types.h | 7 +++++ 2 files changed, 63 insertions(+)