[RFC PATCH v1 2/5] locking/qspinlock: Refactor xchg_tail to use atomic_fetch_and_or
STALE1891d
From: Rui Wang <hidden>
Date: 2021-07-28 11:49:39
Subsystem:
locking primitives, the rest · Maintainers:
Peter Zijlstra, Ingo Molnar, Will Deacon, Boqun Feng, Linus Torvalds
From: wangrui <redacted> Signed-by-off: Rui Wang [off-list ref] Signed-by-off: hev [off-list ref] --- kernel/locking/qspinlock.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-)
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index cbff6ba53d56..350363e14e38 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c@@ -219,22 +219,8 @@ static __always_inline void clear_pending_set_locked(struct qspinlock *lock) */ static __always_inline u32 xchg_tail(struct qspinlock *lock, u32 tail) { - u32 old, new, val = atomic_read(&lock->val); - - for (;;) { - new = (val & _Q_LOCKED_PENDING_MASK) | tail; - /* - * We can use relaxed semantics since the caller ensures that - * the MCS node is properly initialized before updating the - * tail. - */ - old = atomic_cmpxchg_relaxed(&lock->val, val, new); - if (old == val) - break; - - val = old; - } - return old; + const u32 mask = _Q_LOCKED_PENDING_MASK; + return atomic_fetch_and_or_relaxed(mask, tail, &lock->val); } #endif /* _Q_PENDING_BITS == 8 */
--
2.32.0