Messages in this thread | | | Date | Fri, 27 Aug 2021 14:54:39 +0200 | From | Petr Mladek <> | Subject | Re: [RFC PATCH] livepatch: Kick idle cpu's tasks to perform transition |
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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.
> > 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
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