On Thu, 25 Mar 2021, Dong Kai wrote:
> commit 15b2219facad ("kernel: freezer should treat PF_IO_WORKER like
> PF_KTHREAD for freezing") is to fix the freezeing issue of IO threads
> by making the freezer not send them fake signals.
>
> Here live patching consistency model call klp_send_signals to wake up
> all tasks by send fake signal to all non-kthread which only check the
> PF_KTHREAD flag, so it still send signal to io threads which may lead to
> freezeing issue of io threads.
I suppose this could happen, but it will also affect the live patching
transition if the io threads do not react to signals.
Are you able to reproduce it easily? I mean, is there a testcase I could
use to take a closer look?
> Here we take the same fix action by treating PF_IO_WORKERS as PF_KTHREAD
> within klp_send_signal function.
Yes, this sounds reasonable.
Miroslav
> Signed-off-by: Dong Kai <dongkai11@xxxxxxxxxx>
> ---
> note:
> the io threads freeze issue links:
> [1] https://lore.kernel.org/io-uring/YEgnIp43%2F6kFn8GL@xxxxxxxxxxxxxxx/
> [2] https://lore.kernel.org/io-uring/d7350ce7-17dc-75d7-611b-27ebf2cb539b@xxxxxxxxx/
>
> kernel/livepatch/transition.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index f6310f848f34..0e1c35c8f4b4 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -358,7 +358,7 @@ static void klp_send_signals(void)
> * Meanwhile the task could migrate itself and the action
> * would be meaningless. It is not serious though.
> */
> - if (task->flags & PF_KTHREAD) {
> + if (task->flags & (PF_KTHREAD | PF_IO_WORKER)) {
> /*
> * Wake up a kthread which sleeps interruptedly and
> * still has not been migrated.
