On Wed 2021-07-07 14:49:38, Vasily Gorbik wrote:
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.
I see.
quoted hunk ↗ jump to hunk
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
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);
Is this really needed?
+ kick_process(task);
This would probably do the job. Well, I wonder if the following is
a bit cleaner.
wake_up_if_idle(cpu);
Also, please do this in klp_send_signals(). We kick there all other
tasks that block the transition for too long.
Best Regards,
Petr