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

[Yongxin Yang]

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];
+}
+
 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));
 	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.
  *
-- 
2.25.1