diff options
Diffstat (limited to 'arch/arc/kernel/process.c')
| -rw-r--r-- | arch/arc/kernel/process.c | 33 |
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 */ |