From 6b1e76297c4ad4b906fdf054460e4e56914f6e34 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 9 Jun 2017 17:26:33 -0700 Subject: [PATCH] MIPS: cmpxchg: Unify R10000_LLSC_WAR & non-R10000_LLSC_WAR cases Prior to this patch the xchg & cmpxchg functions have duplicated code which is for all intents & purposes identical apart from use of a branch-likely instruction in the R10000_LLSC_WAR case & a regular branch instruction in the non-R10000_LLSC_WAR case. This patch removes the duplication, declaring a __scbeqz macro to select the branch instruction suitable for use when checking the result of an sc instruction & making use of it to unify the 2 cases. In __xchg_u{32,64}() this means writing the branch in asm, where it was previously being done in C as a do...while loop for the non-R10000_LLSC_WAR case. As this is a single instruction, and adds consistency with the R10000_LLSC_WAR cases & the cmpxchg() code, this seems worthwhile. Signed-off-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16348/ Signed-off-by: Ralf Baechle --- arch/mips/include/asm/cmpxchg.h | 80 +++++++++------------------------ 1 file changed, 22 insertions(+), 58 deletions(-) diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h index b71ab4a5fd508..0582c01d229d8 100644 --- a/arch/mips/include/asm/cmpxchg.h +++ b/arch/mips/include/asm/cmpxchg.h @@ -13,44 +13,38 @@ #include #include +/* + * Using a branch-likely instruction to check the result of an sc instruction + * works around a bug present in R10000 CPUs prior to revision 3.0 that could + * cause ll-sc sequences to execute non-atomically. + */ +#if R10000_LLSC_WAR +# define __scbeqz "beqzl" +#else +# define __scbeqz "beqz" +#endif + static inline unsigned long __xchg_u32(volatile int * m, unsigned int val) { __u32 retval; smp_mb__before_llsc(); - if (kernel_uses_llsc && R10000_LLSC_WAR) { + if (kernel_uses_llsc) { unsigned long dummy; __asm__ __volatile__( - " .set arch=r4000 \n" + " .set " MIPS_ISA_ARCH_LEVEL " \n" "1: ll %0, %3 # xchg_u32 \n" " .set mips0 \n" " move %2, %z4 \n" - " .set arch=r4000 \n" + " .set " MIPS_ISA_ARCH_LEVEL " \n" " sc %2, %1 \n" - " beqzl %2, 1b \n" + "\t" __scbeqz " %2, 1b \n" " .set mips0 \n" : "=&r" (retval), "=" GCC_OFF_SMALL_ASM() (*m), "=&r" (dummy) : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) : "memory"); - } else if (kernel_uses_llsc) { - unsigned long dummy; - - do { - __asm__ __volatile__( - " .set "MIPS_ISA_ARCH_LEVEL" \n" - " ll %0, %3 # xchg_u32 \n" - " .set mips0 \n" - " move %2, %z4 \n" - " .set "MIPS_ISA_ARCH_LEVEL" \n" - " sc %2, %1 \n" - " .set mips0 \n" - : "=&r" (retval), "=" GCC_OFF_SMALL_ASM() (*m), - "=&r" (dummy) - : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) - : "memory"); - } while (unlikely(!dummy)); } else { unsigned long flags; @@ -72,34 +66,19 @@ static inline __u64 __xchg_u64(volatile __u64 * m, __u64 val) smp_mb__before_llsc(); - if (kernel_uses_llsc && R10000_LLSC_WAR) { + if (kernel_uses_llsc) { unsigned long dummy; __asm__ __volatile__( - " .set arch=r4000 \n" + " .set " MIPS_ISA_ARCH_LEVEL " \n" "1: lld %0, %3 # xchg_u64 \n" " move %2, %z4 \n" " scd %2, %1 \n" - " beqzl %2, 1b \n" + "\t" __scbeqz " %2, 1b \n" " .set mips0 \n" : "=&r" (retval), "=" GCC_OFF_SMALL_ASM() (*m), "=&r" (dummy) : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) : "memory"); - } else if (kernel_uses_llsc) { - unsigned long dummy; - - do { - __asm__ __volatile__( - " .set "MIPS_ISA_ARCH_LEVEL" \n" - " lld %0, %3 # xchg_u64 \n" - " move %2, %z4 \n" - " scd %2, %1 \n" - " .set mips0 \n" - : "=&r" (retval), "=" GCC_OFF_SMALL_ASM() (*m), - "=&r" (dummy) - : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) - : "memory"); - } while (unlikely(!dummy)); } else { unsigned long flags; @@ -142,24 +121,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz ({ \ __typeof(*(m)) __ret; \ \ - if (kernel_uses_llsc && R10000_LLSC_WAR) { \ - __asm__ __volatile__( \ - " .set push \n" \ - " .set noat \n" \ - " .set arch=r4000 \n" \ - "1: " ld " %0, %2 # __cmpxchg_asm \n" \ - " bne %0, %z3, 2f \n" \ - " .set mips0 \n" \ - " move $1, %z4 \n" \ - " .set arch=r4000 \n" \ - " " st " $1, %1 \n" \ - " beqzl $1, 1b \n" \ - "2: \n" \ - " .set pop \n" \ - : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \ - : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new) \ - : "memory"); \ - } else if (kernel_uses_llsc) { \ + if (kernel_uses_llsc) { \ __asm__ __volatile__( \ " .set push \n" \ " .set noat \n" \ @@ -170,7 +132,7 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz " move $1, %z4 \n" \ " .set "MIPS_ISA_ARCH_LEVEL" \n" \ " " st " $1, %1 \n" \ - " beqz $1, 1b \n" \ + "\t" __scbeqz " $1, 1b \n" \ " .set pop \n" \ "2: \n" \ : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \ @@ -245,4 +207,6 @@ extern void __cmpxchg_called_with_bad_pointer(void); #define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n)) #endif +#undef __scbeqz + #endif /* __ASM_CMPXCHG_H */ -- 2.39.5