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Date: Tue, 28 Jun 2022 04:17:03 -0400 From: guoren@...nel.org To: palmer@...osinc.com, arnd@...db.de, mingo@...hat.com, will@...nel.org, longman@...hat.com, boqun.feng@...il.com Cc: linux-riscv@...ts.infradead.org, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, Guo Ren <guoren@...ux.alibaba.com>, Guo Ren <guoren@...nel.org>, Peter Zijlstra <peterz@...radead.org> Subject: [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read From: Guo Ren <guoren@...ux.alibaba.com> Remove unnecessary atomic_read in arch_spin_value_unlocked(lock), because the value has been in lock. This patch could prevent arch_spin_value_unlocked contend spin_lock data again. Signed-off-by: Guo Ren <guoren@...ux.alibaba.com> Signed-off-by: Guo Ren <guoren@...nel.org> Cc: Peter Zijlstra (Intel) <peterz@...radead.org> Cc: Arnd Bergmann <arnd@...db.de> Cc: Palmer Dabbelt <palmer@...osinc.com> --- include/asm-generic/spinlock.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h index fdfebcb050f4..f1e4fa100f5a 100644 --- a/include/asm-generic/spinlock.h +++ b/include/asm-generic/spinlock.h @@ -84,7 +84,9 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) { - return !arch_spin_is_locked(&lock); + u32 val = lock.counter; + + return ((val >> 16) == (val & 0xffff)); } #include <asm/qrwlock.h> -- 2.36.1
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