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-rw-r--r--arch/arc/kernel/process.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index be1972bd2729..59aa43cb146e 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -41,6 +41,39 @@ SYSCALL_DEFINE0(arc_gettls)
return task_thread_info(current)->thr_ptr;
}
+SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
+{
+ int uval;
+ int ret;
+
+ /*
+ * This is only for old cores lacking LLOCK/SCOND, which by defintion
+ * can't possibly be SMP. Thus doesn't need to be SMP safe.
+ * And this also helps reduce the overhead for serializing in
+ * the UP case
+ */
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
+
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ preempt_disable();
+
+ ret = __get_user(uval, uaddr);
+ if (ret)
+ goto done;
+
+ if (uval != expected)
+ ret = -EAGAIN;
+ else
+ ret = __put_user(new, uaddr);
+
+done:
+ preempt_enable();
+
+ return ret;
+}
+
void arch_cpu_idle(void)
{
/* sleep, but enable all interrupts before committing */