Re: [PATCH v3] PM: hibernate: Log the hibernation mode on entry

[Rafael J. Wysocki (Intel)]

On Tue, Oct 13, 2026 at 3:22 PM Rafael J. Wysocki (Intel)
<rafael@xxxxxxxxxx> wrote:
>
> On Tue, Oct 13, 2026 at 4:34 AM Yongxin Yang <yangyongxin@xxxxxxxxxx> wrote:
> >
> > The hibernation flow is the only place where the kernel decides what
> > to do after a successful image write: hand over to the platform
> > firmware (ACPI S4), power the system off, reboot it, or resume from
> > the image right away. That decision leaves no trace in the log. If the
> > resume path later fails or hangs, the tester cannot tell which outcome
> > was requested, so a report of "the system rebooted instead of powering
> > off" cannot be attributed to configuration or to platform behavior.
> >
> > The mode is selected through /sys/power/disk and stored in
> > hibernation_mode. Append its name to the existing "hibernation entry"
> > message, so that the line reads "hibernation entry (platform)",
> > "hibernation entry (shutdown)", "hibernation entry (reboot)",
> > "hibernation entry (suspend)" or "hibernation entry (test_resume)"
> > instead of a bare "hibernation entry".
> >
> > The names come from hibernation_modes[], the same table that
> > /sys/power/disk uses, through a new hibernation_mode_name() helper, so
> > that the mapping from mode to name lives in one place.
> >
> > No functional change.
> >
> > Signed-off-by: Yongxin Yang <yangyongxin@xxxxxxxxxx>
> > ---
> >  kernel/power/hibernate.c | 32 ++++++++++++++++++++------------
> >  1 file changed, 20 insertions(+), 12 deletions(-)
> >
> > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> > index e365e440cd52..6f88b42b1af8 100644
> > --- a/kernel/power/hibernate.c
> > +++ b/kernel/power/hibernate.c
> > @@ -72,6 +72,24 @@ enum {
> >  #define HIBERNATION_MAX (__HIBERNATION_AFTER_LAST-1)
> >  #define HIBERNATION_FIRST (HIBERNATION_INVALID + 1)
> >
> > +static const char * const hibernation_modes[] = {
> > +       [HIBERNATION_PLATFORM]  = "platform",
> > +       [HIBERNATION_SHUTDOWN]  = "shutdown",
> > +       [HIBERNATION_REBOOT]    = "reboot",
> > +#ifdef CONFIG_SUSPEND
> > +       [HIBERNATION_SUSPEND]   = "suspend",
> > +#endif
> > +       [HIBERNATION_TEST_RESUME]       = "test_resume",
> > +};
> > +
> > +static const char *hibernation_mode_name(int mode)
> > +{
> > +       if (mode < HIBERNATION_FIRST || mode > HIBERNATION_MAX)
> > +               return "unknown";
> > +
> > +       return hibernation_modes[mode];
> > +}
>
> Thanks for the update, but I really meant this:
>
> static const char *hibernation_mode_name(int mode)
> {
>         switch (mode) {
>         case HIBERNATION_PLATFORM:
>                 return "platform";
>         case HIBERNATION_SHUTDOWN:
>                 return "shutdown";
>         case HIBERNATION_REBOOT:
>                 return "reboot";
>         case HIBERNATION_TEST_RESUME:
>                 return "test_resume";
> #ifdef CONFIG_SUSPEND
>         case HIBERNATION_SUSPEND:
>                 return "suspend";
> #endif
>         }
>         return "unknown";
> }

OK, scratch this.

The table is already there, so it can be used below.

> > +
> >  static int hibernation_mode = HIBERNATION_SHUTDOWN;
> >
> >  bool freezer_test_done;
> > @@ -794,7 +812,8 @@ int hibernate(void)
> >                 goto Unlock;
> >         }
> >
> > -       pr_info("hibernation entry\n");
> > +       pr_info("hibernation entry (%s)\n",
> > +               hibernation_mode_name(hibernation_mode));

But is the wrapper function really needed here?

> >         pm_prepare_console();
> >         error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
> >         if (error)
> > @@ -1130,17 +1149,6 @@ static int __init software_resume_initcall(void)
> >  }
> >  late_initcall_sync(software_resume_initcall);
> >
> > -
> > -static const char * const hibernation_modes[] = {
> > -       [HIBERNATION_PLATFORM]  = "platform",
> > -       [HIBERNATION_SHUTDOWN]  = "shutdown",
> > -       [HIBERNATION_REBOOT]    = "reboot",
> > -#ifdef CONFIG_SUSPEND
> > -       [HIBERNATION_SUSPEND]   = "suspend",
> > -#endif
> > -       [HIBERNATION_TEST_RESUME]       = "test_resume",
> > -};
> > -
> >  /*
> >   * /sys/power/disk - Control hibernation mode.
> >   *
> > --