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Diffstat (limited to 'arch/arm64/include/asm/spinlock.h')
-rw-r--r--arch/arm64/include/asm/spinlock.h69
1 files changed, 7 insertions, 62 deletions
diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index cae331d553f8..95ad7102b63c 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -26,58 +26,6 @@
* The memory barriers are implicit with the load-acquire and store-release
* instructions.
*/
-static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
-{
- unsigned int tmp;
- arch_spinlock_t lockval;
- u32 owner;
-
- /*
- * Ensure prior spin_lock operations to other locks have completed
- * on this CPU before we test whether "lock" is locked.
- */
- smp_mb();
- owner = READ_ONCE(lock->owner) << 16;
-
- asm volatile(
-" sevl\n"
-"1: wfe\n"
-"2: ldaxr %w0, %2\n"
- /* Is the lock free? */
-" eor %w1, %w0, %w0, ror #16\n"
-" cbz %w1, 3f\n"
- /* Lock taken -- has there been a subsequent unlock->lock transition? */
-" eor %w1, %w3, %w0, lsl #16\n"
-" cbz %w1, 1b\n"
- /*
- * The owner has been updated, so there was an unlock->lock
- * transition that we missed. That means we can rely on the
- * store-release of the unlock operation paired with the
- * load-acquire of the lock operation to publish any of our
- * previous stores to the new lock owner and therefore don't
- * need to bother with the writeback below.
- */
-" b 4f\n"
-"3:\n"
- /*
- * Serialise against any concurrent lockers by writing back the
- * unlocked lock value
- */
- ARM64_LSE_ATOMIC_INSN(
- /* LL/SC */
-" stxr %w1, %w0, %2\n"
- __nops(2),
- /* LSE atomics */
-" mov %w1, %w0\n"
-" cas %w0, %w0, %2\n"
-" eor %w1, %w1, %w0\n")
- /* Somebody else wrote to the lock, GOTO 10 and reload the value */
-" cbnz %w1, 2b\n"
-"4:"
- : "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
- : "r" (owner)
- : "memory");
-}
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
@@ -176,7 +124,11 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
- smp_mb(); /* See arch_spin_unlock_wait */
+ /*
+ * Ensure prior spin_lock operations to other locks have completed
+ * on this CPU before we test whether "lock" is locked.
+ */
+ smp_mb(); /* ^^^ */
return !arch_spin_value_unlocked(READ_ONCE(*lock));
}
@@ -358,14 +310,7 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
#define arch_read_relax(lock) cpu_relax()
#define arch_write_relax(lock) cpu_relax()
-/*
- * Accesses appearing in program order before a spin_lock() operation
- * can be reordered with accesses inside the critical section, by virtue
- * of arch_spin_lock being constructed using acquire semantics.
- *
- * In cases where this is problematic (e.g. try_to_wake_up), an
- * smp_mb__before_spinlock() can restore the required ordering.
- */
-#define smp_mb__before_spinlock() smp_mb()
+/* See include/linux/spinlock.h */
+#define smp_mb__after_spinlock() smp_mb()
#endif /* __ASM_SPINLOCK_H */