Re: [PATCH RESEND v3] PM: hibernate: Avoid missing wakeup events during hibernation

["Rafael J. Wysocki" <rafael@kernel.org>]

On Mon, Dec 4, 2023 at 3:12 AM Chris Feng <chris.feng@mediatek.com> wrote:
>
> Wakeup events that occur in the hibernation process's
> hibernation_platform_enter() cannot wake up the system. Although the
> current hibernation framework will execute part of the recovery process
> after a wakeup event occurs, it ultimately performs a shutdown operation
> because the system does not check the return value of
> hibernation_platform_enter(). In short, if a wakeup event occurs before
> putting the system into the final low-power state, it will be missed.
>
> To solve this problem, check the return value of
> hibernation_platform_enter(). When it returns -EAGAIN or -EBUSY (indicate
> the occurrence of a wakeup event), execute the hibernation recovery
> process, discard the previously saved image, and ultimately return to the
> working state.
>
> Signed-off-by: Chris Feng <chris.feng@mediatek.com>
> ---
> [PATCH v2]:
>  - Optimize the "if" condition logic.
>  - Link to v1: https://lore.kernel.org/all/20231024091447.108072-1-chris.feng@mediatek.com
> [PATCH v3]:
>  - Use pr_info instead of pr_err.
>  - Fix undeclared function 'swsusp_unmark' build error.
>  - Refine commit and printing message.
>  - Change the subject.
>  - Link to v2: https://lore.kernel.org/all/20231120081516.55172-1-chris.feng@mediatek.com
> ---
>  kernel/power/hibernate.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 8d35b9f9aaa3..fb3b63e178b0 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -642,9 +642,9 @@ int hibernation_platform_enter(void)
>   */
>  static void power_down(void)
>  {
> -#ifdef CONFIG_SUSPEND
>         int error;
>
> +#ifdef CONFIG_SUSPEND
>         if (hibernation_mode == HIBERNATION_SUSPEND) {
>                 error = suspend_devices_and_enter(mem_sleep_current);
>                 if (error) {
> @@ -667,7 +667,15 @@ static void power_down(void)
>                 kernel_restart(NULL);
>                 break;
>         case HIBERNATION_PLATFORM:
> -               hibernation_platform_enter();
> +               error = hibernation_platform_enter();
> +               if (error == -EAGAIN || error == -EBUSY) {
> +#ifdef CONFIG_SUSPEND
> +                       swsusp_unmark();
> +#endif

It would be somewhat cleaner to define an empty stub of
swsusp_unmark() for the CONFIG_SUSPEND undefined case in the header
file.

> +                       events_check_enabled = false;
> +                       pr_info("Hibernation process aborted due to detected wakeup event.\n");
> +                       return;
> +               }
>                 fallthrough;
>         case HIBERNATION_SHUTDOWN:
>                 if (kernel_can_power_off())
> --