From c5acdf12cc24d34ea3f9426472dcb3f5d581b1e5 Mon Sep 17 00:00:00 2001 From: Guo Ren Date: Wed, 13 Apr 2022 15:27:52 +0800 Subject: [PATCH] csky: atomic: Add conditional atomic operations' optimization Add conditional atomic operations' optimization: - arch_atomic_fetch_add_unless - arch_atomic_inc_unless_negative - arch_atomic_dec_unless_positive - arch_atomic_dec_if_positive Comments by Boqun: FWIW, you probably need to make sure that a barrier instruction inside an lr/sc loop is a good thing. IIUC, the execution time of a barrier instruction is determined by the status of store buffers and invalidate queues (and probably other stuffs), so it may increase the execution time of the lr/sc loop, and make it unlikely to succeed. But this really depends on how the arch executes these instructions. Signed-off-by: Guo Ren Signed-off-by: Guo Ren Cc: Boqun Feng --- arch/csky/include/asm/atomic.h | 95 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) diff --git a/arch/csky/include/asm/atomic.h b/arch/csky/include/asm/atomic.h index 56c9dc8..60406ef 100644 --- a/arch/csky/include/asm/atomic.h +++ b/arch/csky/include/asm/atomic.h @@ -100,6 +100,101 @@ ATOMIC_OPS(xor) #undef ATOMIC_FETCH_OP +static __always_inline int +arch_atomic_fetch_add_unless(atomic_t *v, int a, int u) +{ + int prev, tmp; + + __asm__ __volatile__ ( + RELEASE_FENCE + "1: ldex.w %0, (%3) \n" + " cmpne %0, %4 \n" + " bf 2f \n" + " mov %1, %0 \n" + " add %1, %2 \n" + " stex.w %1, (%3) \n" + " bez %1, 1b \n" + FULL_FENCE + "2:\n" + : "=&r" (prev), "=&r" (tmp) + : "r" (a), "r" (&v->counter), "r" (u) + : "memory"); + + return prev; +} +#define arch_atomic_fetch_add_unless arch_atomic_fetch_add_unless + +static __always_inline bool +arch_atomic_inc_unless_negative(atomic_t *v) +{ + int rc, tmp; + + __asm__ __volatile__ ( + RELEASE_FENCE + "1: ldex.w %0, (%2) \n" + " movi %1, 0 \n" + " blz %0, 2f \n" + " movi %1, 1 \n" + " addi %0, 1 \n" + " stex.w %0, (%2) \n" + " bez %0, 1b \n" + FULL_FENCE + "2:\n" + : "=&r" (tmp), "=&r" (rc) + : "r" (&v->counter) + : "memory"); + + return tmp ? true : false; + +} +#define arch_atomic_inc_unless_negative arch_atomic_inc_unless_negative + +static __always_inline bool +arch_atomic_dec_unless_positive(atomic_t *v) +{ + int rc, tmp; + + __asm__ __volatile__ ( + RELEASE_FENCE + "1: ldex.w %0, (%2) \n" + " movi %1, 0 \n" + " bhz %0, 2f \n" + " movi %1, 1 \n" + " subi %0, 1 \n" + " stex.w %0, (%2) \n" + " bez %0, 1b \n" + FULL_FENCE + "2:\n" + : "=&r" (tmp), "=&r" (rc) + : "r" (&v->counter) + : "memory"); + + return tmp ? true : false; +} +#define arch_atomic_dec_unless_positive arch_atomic_dec_unless_positive + +static __always_inline int +arch_atomic_dec_if_positive(atomic_t *v) +{ + int dec, tmp; + + __asm__ __volatile__ ( + RELEASE_FENCE + "1: ldex.w %0, (%2) \n" + " subi %1, %0, 1 \n" + " blz %1, 2f \n" + " stex.w %1, (%2) \n" + " bez %1, 1b \n" + FULL_FENCE + "2:\n" + : "=&r" (dec), "=&r" (tmp) + : "r" (&v->counter) + : "memory"); + + return dec - 1; +} +#define arch_atomic_dec_if_positive arch_atomic_dec_if_positive + #define ATOMIC_OP() \ static __always_inline \ int arch_atomic_xchg_relaxed(atomic_t *v, int n) \ -- 2.7.4