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Subject[tip: sched/core] sched,livepatch: Use wake_up_if_idle()
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 5de62ea84abd732ded7c5569426fd71c0420f83e
Gitweb: https://git.kernel.org/tip/5de62ea84abd732ded7c5569426fd71c0420f83e
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 21 Sep 2021 22:16:02 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 14 Oct 2021 13:09:25 +02:00

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
---
include/linux/sched/idle.h | 4 ++++
kernel/livepatch/transition.c | 5 ++++-
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched/idle.h b/include/linux/sched/idle.h
index 22873d2..d73d314 100644
--- 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
--- 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);
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