[PATCHv4 3/3] watchdog/softlockup: add SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob

[Bitao Hu]

The interrupt storm detection mechanism we implemented requires a
considerable amount of global storage space when configured for
the maximum number of CPUs.
Therefore, adding a SOFTLOCKUP_DETECTOR_INTR_STORM Kconfig knob that
defaults to "yes" if the max number of CPUs is <= 128.

Signed-off-by: Bitao Hu <yaoma@xxxxxxxxxxxxxxxxx>
---
 kernel/watchdog.c |  2 +-
 lib/Kconfig.debug | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d31120c3e9d1..a2722935a381 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -338,7 +338,7 @@ __setup("watchdog_thresh=", watchdog_thresh_setup);
 
 static void __lockup_detector_cleanup(void);
 
-#ifdef CONFIG_IRQ_TIME_ACCOUNTING
+#ifdef CONFIG_SOFTLOCKUP_DETECTOR_INTR_STORM
 #define NUM_STATS_GROUPS	5
 enum stats_per_group {
 	STATS_SYSTEM,
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 975a07f9f1cc..74002ba7c42d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1029,6 +1029,19 @@ config SOFTLOCKUP_DETECTOR
 	  chance to run.  The current stack trace is displayed upon
 	  detection and the system will stay locked up.
 
+config SOFTLOCKUP_DETECTOR_INTR_STORM
+	bool "Detect Interrupt Storm in Soft Lockups"
+	depends on SOFTLOCKUP_DETECTOR && IRQ_TIME_ACCOUNTING
+	default y if NR_CPUS <= 128
+	help
+	  Say Y here to enable the kernel to detect interrupt storm
+	  during "soft lockups".
+
+	  "soft lockups" can be caused by a variety of reasons. If one is caused by
+	  an interrupt storm, then the storming interrupts will not be on the
+	  callstack. To detect this case, it is necessary to report the CPU stats
+	  and the interrupt counts during the "soft lockups".
+
 config BOOTPARAM_SOFTLOCKUP_PANIC
 	bool "Panic (Reboot) On Soft Lockups"
 	depends on SOFTLOCKUP_DETECTOR
-- 
2.37.1 (Apple Git-137.1)