From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> Using arch_spinlock_is_locked would cause another unnecessary memory access to the contended value. Although it won't cause a significant performance gap in most architectures, the arch_spin_value_unlocked argument contains enough information. Thus, remove unnecessary atomic_read in arch_spin_value_unlocked(). Signed-off-by: Guo Ren <guoren@xxxxxxxxxx> Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> Cc: David Laight <David.Laight@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> --- Changelog: This patch is separate from: https://lore.kernel.org/linux-riscv/20220808071318.3335746-1-guoren@xxxxxxxxxx/ Peter & David have commented on it: https://lore.kernel.org/linux-riscv/YsK4Z9w0tFtgkni8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ --- include/asm-generic/spinlock.h | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h index fdfebcb050f4..90803a826ba0 100644 --- a/include/asm-generic/spinlock.h +++ b/include/asm-generic/spinlock.h @@ -68,11 +68,18 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) smp_store_release(ptr, (u16)val + 1); } +static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) +{ + u32 val = lock.counter; + + return ((val >> 16) == (val & 0xffff)); +} + static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock) { - u32 val = atomic_read(lock); + arch_spinlock_t val = READ_ONCE(*lock); - return ((val >> 16) != (val & 0xffff)); + return !arch_spin_value_unlocked(val); } static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) @@ -82,11 +89,6 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) return (s16)((val >> 16) - (val & 0xffff)) > 1; } -static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) -{ - return !arch_spin_is_locked(&lock); -} - #include <asm/qrwlock.h> #endif /* __ASM_GENERIC_SPINLOCK_H */ -- 2.36.1
