There are four possible variants of hardlockup detectors:
+ buddy: available when SMP is set.
+ perf: available when HAVE_HARDLOCKUP_DETECTOR_PERF is set.
+ arch-specific: available when HAVE_HARDLOCKUP_DETECTOR_ARCH is set.
+ sparc64 special variant: available when HAVE_NMI_WATCHDOG is set
and HAVE_HARDLOCKUP_DETECTOR_ARCH is not set.
The check for the sparc64 variant is more complicated because
HAVE_NMI_WATCHDOG is used to #ifdef code used by both arch-specific
and sparc64 specific variant. Therefore it is automatically
selected with HAVE_HARDLOCKUP_DETECTOR_ARCH.
This complexity is partly hidden in HAVE_HARDLOCKUP_DETECTOR_NON_ARCH.
It reduces the size of some checks but it makes them harder to follow.
Finally, the other temporary variable HARDLOCKUP_DETECTOR_NON_ARCH
is used to re-compute HARDLOCKUP_DETECTOR_PERF/BUDDY when the global
HARDLOCKUP_DETECTOR switch is enabled/disabled.
Make the logic more straightforward by the following changes:
+ Better explain the role of HAVE_HARDLOCKUP_DETECTOR_ARCH and
HAVE_NMI_WATCHDOG in comments.
+ Add HAVE_HARDLOCKUP_DETECTOR_BUDDY so that there is separate
HAVE_* for all four hardlockup detector variants.
Use it in the other conditions instead of SMP. It makes it
clear that it is about the buddy detector.
+ Open code HAVE_HARDLOCKUP_DETECTOR_NON_ARCH in HARDLOCKUP_DETECTOR
and HARDLOCKUP_DETECTOR_PREFER_BUDDY. It helps to understand
the conditions between the four hardlockup detector variants.
+ Define the exact conditions when HARDLOCKUP_DETECTOR_PERF/BUDDY
can be enabled. It explains the dependency on the other
hardlockup detector variants.
Also it allows to remove HARDLOCKUP_DETECTOR_NON_ARCH by using "imply".
It triggers re-evaluating HARDLOCKUP_DETECTOR_PERF/BUDDY when
the global HARDLOCKUP_DETECTOR switch is changed.
+ Add dependency on HARDLOCKUP_DETECTOR so that the affected variables
disappear when the hardlockup detectors are disabled.
Another nice side effect is that HARDLOCKUP_DETECTOR_PREFER_BUDDY
value is not preserved when the global switch is disabled.
The user has to make the decision again when it gets re-enabled.
Signed-off-by: Petr Mladek
---
arch/Kconfig | 23 +-
lib/Kconfig.debug | 62 +++
2 files changed, 53 insertions(+), 32 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 422f0ffa269e..77e5af5fda3f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -404,17 +404,28 @@ config HAVE_NMI_WATCHDOG
depends on HAVE_NMI
bool
help
- The arch provides a low level NMI watchdog. It provides
- asm/nmi.h, and defines its own watchdog_hardlockup_probe() and
- arch_touch_nmi_watchdog().
+ The arch provides its own hardlockup detector implementation instead
+ of the generic ones.
+
+ Sparc64 defines this variable without HAVE_HARDLOCKUP_DETECTOR_ARCH.
+ It is the last arch-specific implementation which was developed before
+ adding the common infrastructure for handling hardlockup detectors.
+ It is always built. It does _not_ use the common command line
+ parameters and sysctl interface, except for
+ /proc/sys/kernel/nmi_watchdog.
config HAVE_HARDLOCKUP_DETECTOR_ARCH
bool
select HAVE_NMI_WATCHDOG
help
- The arch chooses to provide its own hardlockup detector, which is
- a superset of the HAVE_NMI_WATCHDOG. It also conforms to config
- interfaces and parameters provided by hardlockup detector subsystem.
+ The arch provides its own hardlockup detector implementation instead
+ of the generic ones.
+
+ It uses the same command line parameters, and sysctl interface,
+ as the generic hardlockup detectors.
+
+ HAVE_NMI_WATCHDOG is selected to build the code shared with
+ the sparc64 specific implementation.
config HAVE_PERF_REGS
bool
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3e91fa33c7a0..a0b0c4decb89 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1035,16 +1035,33 @@ config BOOTPARAM_SOFTLOCKUP_PANIC
Say N if unsure.
+config HAVE_HARDLOCKUP_DETECTOR_BUDDY
+ bool
+ depends on SMP
+ default y
+
#
-# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
-# lockup detector rather than the perf based detector.
+# Global switch whether to build a hardlockup detector at all. It is available
+# only when the architecture supports at least one implementation. There are
+# two exceptions. The hardlockup detector is never enabled on:
+#
+# s390: it reported many false positives there
+#
+# sparc64: has a custom implementation which is not using the common
+# hardlockup command line options and sysctl interface.
+#
+# Note that HAVE_NMI_WATCHDOG is used to distinguish the
