[PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read

guoren
2022-06-28T08:19:19Z

From: Guo Ren <guoren@linux.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@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@rivosinc.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