Re: [RFC PATCH] livepatch: Kick idle cpu's tasks to perform transition
From: Petr Mladek <pmladek@suse.com>
Date: 2021-08-27 12:54:43
Also in:
lkml
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