[PATCH] ARM SMP: Use exclusive load/store for __xchg
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/include/asm-arm/system.h b/include/asm-arm/system.h
index 2f44b20..3f9c362 100644
--- a/include/asm-arm/system.h
+++ b/include/asm-arm/system.h
@@ -323,12 +323,8 @@
* NOTE that this solution won't work on an SMP system, so explcitly
* forbid it here.
*/
-#ifdef CONFIG_SMP
-#error SMP is not supported on SA1100/SA110
-#else
#define swp_is_buggy
#endif
-#endif
static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
{
@@ -337,35 +333,68 @@
#ifdef swp_is_buggy
unsigned long flags;
#endif
+#if __LINUX_ARM_ARCH__ >= 6
+ unsigned int tmp;
+#endif
switch (size) {
-#ifdef swp_is_buggy
- case 1:
- local_irq_save(flags);
- ret = *(volatile unsigned char *)ptr;
- *(volatile unsigned char *)ptr = x;
- local_irq_restore(flags);
- break;
-
- case 4:
- local_irq_save(flags);
- ret = *(volatile unsigned long *)ptr;
- *(volatile unsigned long *)ptr = x;
- local_irq_restore(flags);
- break;
-#else
- case 1: __asm__ __volatile__ ("swpb %0, %1, [%2]"
- : "=&r" (ret)
- : "r" (x), "r" (ptr)
- : "memory", "cc");
- break;
- case 4: __asm__ __volatile__ ("swp %0, %1, [%2]"
- : "=&r" (ret)
- : "r" (x), "r" (ptr)
- : "memory", "cc");
- break;
+#if __LINUX_ARM_ARCH__ >= 6
+ case 1:
+ asm volatile("@ __xchg1\n"
+ "1: ldrexb %0, [%3]\n"
+ " strexb %1, %2, [%3]\n"
+ " teq %1, #0\n"
+ " bne 1b"
+ : "=&r" (ret), "=&r" (tmp)
+ : "r" (x), "r" (ptr)
+ : "memory", "cc");
+ break;
+ case 4:
+ asm volatile("@ __xchg4\n"
+ "1: ldrex %0, [%3]\n"
+ " strex %1, %2, [%3]\n"
+ " teq %1, #0\n"
+ " bne 1b"
+ : "=&r" (ret), "=&r" (tmp)
+ : "r" (x), "r" (ptr)
+ : "memory", "cc");
+ break;
+#elif defined(swp_is_buggy)
+#ifdef CONFIG_SMP
+#error SMP is not supported on this platform
#endif
- default: __bad_xchg(ptr, size), ret = 0;
+ case 1:
+ local_irq_save(flags);
+ ret = *(volatile unsigned char *)ptr;
+ *(volatile unsigned char *)ptr = x;
+ local_irq_restore(flags);
+ break;
+
+ case 4:
+ local_irq_save(flags);
+ ret = *(volatile unsigned long *)ptr;
+ *(volatile unsigned long *)ptr = x;
+ local_irq_restore(flags);
+ break;
+#else
+ case 1:
+ asm volatile("@ __xchg1\n"
+ " swpb %0, %1, [%2]"
+ : "=&r" (ret)
+ : "r" (x), "r" (ptr)
+ : "memory", "cc");
+ break;
+ case 4:
+ asm volatile("@ __xchg4\n"
+ " swp %0, %1, [%2]"
+ : "=&r" (ret)
+ : "r" (x), "r" (ptr)
+ : "memory", "cc");
+ break;
+#endif
+ default:
+ __bad_xchg(ptr, size), ret = 0;
+ break;
}
return ret;