On an idle system with large amount of cpus it might happen that
klp_update_patch_state() is not reached in do_idle() for a long periods
of time. With debug messages enabled log is filled with:
[ 499.442643] livepatch: klp_try_switch_task: swapper/63:0 is running
without any signs of progress. Ending up with "failed to complete
transition".
On s390 LPAR with 128 cpus not a single transition is able to complete
and livepatch kselftests fail.
To deal with that, make sure we break out of do_idle() inner loop to
reach klp_update_patch_state() by marking idle tasks as NEED_RESCHED
as well as kick cpus out of idle state.
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
---
kernel/livepatch/transition.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index 3a4beb9395c4..793eba46e970 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -415,8 +415,11 @@ 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;
+ set_tsk_need_resched(task);
+ kick_process(task);
+ }
} else if (task->patch_state != klp_target_state) {
/* offline idle tasks can be switched immediately */
clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
--
2.25.4
