To prevent GCC clobbering one of the inputs and
to make this cross arch compatible, we use C11 atomics.
The packed struct containing a lock is unpacked to fix alignment.
---
i386/i386/irq.c | 2 +-
i386/i386/lock.h | 26 +++++++++++---------------
kern/lock.h | 4 ++--
3 files changed, 14 insertions(+), 18 deletions(-)
diff --git a/i386/i386/irq.c b/i386/i386/irq.c
index ea10e179..8b89b70d 100644
--- a/i386/i386/irq.c
+++ b/i386/i386/irq.c
@@ -39,7 +39,7 @@ struct nested_irq {
simple_lock_irq_data_t irq_lock; /* Protects ndisabled */
int32_t ndisabled;
uint32_t unused[14];
-} __attribute__((packed)) nested_irqs[NINTR];
+} nested_irqs[NINTR];
void
init_irqs (void)
diff --git a/i386/i386/lock.h b/i386/i386/lock.h
index 0384536a..c086e9b5 100644
--- a/i386/i386/lock.h
+++ b/i386/i386/lock.h
@@ -33,11 +33,11 @@
{.lock_data = 0}
#if NCPUS > 1
+#include <stdatomic.h>
#include <i386/smp.h>
/*
- * All of the locking routines are built from calls on
- * a locked-exchange operation. Values of the lock are
+ * Values of the lock are
* 0 for unlocked, 1 for locked.
*/
@@ -47,31 +47,27 @@
* The code here depends on the GNU C compiler.
*/
-#define _simple_lock_xchg_(lock, new_val) \
-({ natural_t _old_val_; \
- asm volatile("xchg %0, %2" \
- : "=r" (_old_val_) \
- : "0" ((natural_t)(new_val)), "m" (*(lock)) : "memory" \
- ); \
- _old_val_; \
- })
-
#define simple_lock_init(l) \
((l)->lock_data = 0)
#define _simple_lock(l) \
({ \
- while(_simple_lock_xchg_(l, 1)) \
- while (*(volatile natural_t *)&(l)->lock_data) \
+ for (;;) { \
+ if (!atomic_exchange_explicit(&(l)->lock_data, 1,
__ATOMIC_ACQUIRE)) \
+ break; \
+ while (atomic_load_explicit(&(l)->lock_data, __ATOMIC_RELAXED)) \
cpu_pause(); \
+ } \
0; \
})
#define _simple_unlock(l) \
- (_simple_lock_xchg_(l, 0))
+ atomic_store_explicit(&(l)->lock_data, 0, __ATOMIC_RELEASE)
#define _simple_lock_try(l) \
- (!_simple_lock_xchg_(l, 1))
+ (!atomic_load_explicit(&(l)->lock_data, __ATOMIC_RELAXED) && \
+ !atomic_exchange_explicit(&(l)->lock_data, 1, __ATOMIC_ACQUIRE))
+
/*
* General bit-lock routines.
diff --git a/kern/lock.h b/kern/lock.h
index 74f2e26e..38111ed0 100644
--- a/kern/lock.h
+++ b/kern/lock.h
@@ -58,6 +58,7 @@
* MACH_LDEBUG is set.
*/
+#include <stdatomic.h>
#include <machine/lock.h>/*XXX*/
#if NCPUS > 1
#if MACH_LOCK_MON == 0
@@ -76,9 +77,8 @@
/*
* A simple spin lock.
*/
-
struct slock {
- volatile natural_t lock_data; /* in general 1 bit is sufficient */
+ atomic_uint lock_data; /* in general 1 bit is sufficient */
struct {} is_a_simple_lock;
};
--
2.45.2
