[PATCH v6 4/9] csky: locks: Optimize coding convention

guoren
2021-03-31T14:32:37Z

From: Guo Ren <guoren@linux.alibaba.com>

- Using smp_cond_load_acquire in arch_spin_lock by Peter's
advice.
- Using __smp_acquire_fence in arch_spin_trylock
- Using smp_store_release in arch_spin_unlock

All above are just coding conventions and won't affect the
function.

TODO in smp_cond_load_acquire for architecture:
- current csky only has:
lr.w val, <p0>
sc.w <p0>. val2
(Any other stores to p0 will let sc.w failed)

- But smp_cond_load_acquire need:
lr.w val, <p0>
wfe
(Any stores to p0 will send the event to let wfe retired)

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Link: https://lore.kernel.org/linux-riscv/CAAhSdy1JHLUFwu7RuCaQ+RUWRBks2KsDva7EpRt8--4ZfofSUQ@mail.gmail.com/T/#m13adac285b7f51f4f879a5d6b65753ecb1a7524e
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
---
arch/csky/include/asm/spinlock.h | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h
index 69f5aa249c5f..69677167977a 100644
--- a/arch/csky/include/asm/spinlock.h
+++ b/arch/csky/include/asm/spinlock.h
@@ -26,10 +26,8 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
: "r"(p), "r"(ticket_next)
: "cc");

- while (lockval.tickets.next != lockval.tickets.owner)
- lockval.tickets.owner = READ_ONCE(lock->tickets.owner);
-
- smp_mb();
+ smp_cond_load_acquire(&lock->tickets.owner,
+ VAL == lockval.tickets.next);
}

static inline int arch_spin_trylock(arch_spinlock_t *lock)
@@ -55,15 +53,14 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
} while (!res);

if (!contended)
- smp_mb();
+ __smp_acquire_fence();

return !contended;
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
- smp_mb();
- WRITE_ONCE(lock->tickets.owner, lock->tickets.owner + 1);
+ smp_store_release(&lock->tickets.owner, lock->tickets.owner + 1);
}

static inline int arch_spin_value_unlocked(arch_spinlock_t lock)