sched,livepatch: Use wake_up_if_idle()

Make sure to prod idle CPUs so they call klp_update_patch_state().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929151723.162004989@infradead.org

diff --git a/include/linux/sched/idle.h b/include/linux/sched/idle.h
index 22873d2..d73d314 100644 (file)
--- a/include/linux/sched/idle.h
+++ b/include/linux/sched/idle.h
@@ -11,7 +11,11 @@ enum cpu_idle_type {
        CPU_MAX_IDLE_TYPES
 };
 
+#ifdef CONFIG_SMP
 extern void wake_up_if_idle(int cpu);
+#else
+static inline void wake_up_if_idle(int cpu) { }
+#endif
 
 /*
  * Idle thread specific functions to determine the need_resched

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 75251e9..5683ac0 100644 (file)
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -413,8 +413,11 @@ void klp_try_complete_transition(void)
        for_each_possible_cpu(cpu) {
                task = idle_task(cpu);
                if (cpu_online(cpu)) {
-                       if (!klp_try_switch_task(task))
+                       if (!klp_try_switch_task(task)) {
                                complete = false;
+                               /* Make idle task go through the main loop. */
+                               wake_up_if_idle(cpu);
+                       }
                } else if (task->patch_state != klp_target_state) {
                        /* offline idle tasks can be switched immediately */
                        clear_tsk_thread_flag(task, TIF_PATCH_PENDING);