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authorPetr Mladek <pmladek@suse.com>2023-06-16 17:06:14 +0200
committerAndrew Morton <akpm@linux-foundation.org>2023-06-19 16:25:28 -0700
commit1356d0b966e7ed81832af35478b913495cf7792e (patch)
tree62e920c9e489f01a51b7c2f5e631d713ec85a47c /lib
parent4917a25f83a8dc95eafd0107be87d4340f48d265 (diff)
watchdog/hardlockup: make the config checks more straightforward
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. Link: https://lkml.kernel.org/r/20230616150618.6073-3-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Douglas Anderson <dianders@chromium.org> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: "David S. Miller" <davem@davemloft.net> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug62
1 files changed, 36 insertions, 26 deletions
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
+
+#
+# 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:
#
-# arch/ can define HAVE_HARDLOCKUP_DETECTOR_ARCH to provide their own hard
-# lockup detector rather than the perf based detector.
+# 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 sparc64 specific
+# implementaion. It is automatically enabled also for other arch-specific
+# variants which set HAVE_HARDLOCKUP_DETECTOR_ARCH. It makes the check
+# of avaialable and supported variants quite tricky.
#
config HARDLOCKUP_DETECTOR
bool "Detect Hard Lockups"
depends on DEBUG_KERNEL && !S390
- depends on HAVE_HARDLOCKUP_DETECTOR_NON_ARCH || HAVE_HARDLOCKUP_DETECTOR_ARCH
+ depends on ((HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY) && !HAVE_NMI_WATCHDOG) || HAVE_HARDLOCKUP_DETECTOR_ARCH
+ imply HARDLOCKUP_DETECTOR_PERF
+ imply HARDLOCKUP_DETECTOR_BUDDY
select LOCKUP_DETECTOR
- select HARDLOCKUP_DETECTOR_NON_ARCH if HAVE_HARDLOCKUP_DETECTOR_NON_ARCH
help
Say Y here to enable the kernel to act as a watchdog to detect
@@ -1055,9 +1072,14 @@ config HARDLOCKUP_DETECTOR
chance to run. The current stack trace is displayed upon detection
and the system will stay locked up.
+#
+# Note that arch-specific variants are always preferred.
+#
config HARDLOCKUP_DETECTOR_PREFER_BUDDY
bool "Prefer the buddy CPU hardlockup detector"
- depends on HAVE_HARDLOCKUP_DETECTOR_PERF && SMP
+ depends on HARDLOCKUP_DETECTOR
+ depends on HAVE_HARDLOCKUP_DETECTOR_PERF && HAVE_HARDLOCKUP_DETECTOR_BUDDY
+ depends on !HAVE_NMI_WATCHDOG
help
Say Y here to prefer the buddy hardlockup detector over the perf one.
@@ -1071,39 +1093,27 @@ config HARDLOCKUP_DETECTOR_PREFER_BUDDY
config HARDLOCKUP_DETECTOR_PERF
bool
- depends on HAVE_HARDLOCKUP_DETECTOR_PERF
+ depends on HARDLOCKUP_DETECTOR
+ depends on HAVE_HARDLOCKUP_DETECTOR_PERF && !HARDLOCKUP_DETECTOR_PREFER_BUDDY
+ depends on !HAVE_NMI_WATCHDOG
select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER
config HARDLOCKUP_DETECTOR_BUDDY
bool
- depends on SMP
+ depends on HARDLOCKUP_DETECTOR
+ depends on HAVE_HARDLOCKUP_DETECTOR_BUDDY
+ depends on !HAVE_HARDLOCKUP_DETECTOR_PERF || HARDLOCKUP_DETECTOR_PREFER_BUDDY
+ depends on !HAVE_NMI_WATCHDOG
select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER
+#
# Both the "perf" and "buddy" hardlockup detectors count hrtimer
# interrupts. This config enables functions managing this common code.
+#
config HARDLOCKUP_DETECTOR_COUNTS_HRTIMER
bool
select SOFTLOCKUP_DETECTOR
-# For hardlockup detectors you can have one directly provided by the arch
-# or use a "non-arch" one. If you're using a "non-arch" one that is
-# further divided the perf hardlockup detector (which, confusingly, needs
-# arch-provided perf support) and the buddy hardlockup detector (which just
-# needs SMP). In either case, using the "non-arch" code conflicts with
-# the NMI watchdog code (which is sometimes used directly and sometimes used
-# by the arch-provided hardlockup detector).
-config HAVE_HARDLOCKUP_DETECTOR_NON_ARCH
- bool
- depends on (HAVE_HARDLOCKUP_DETECTOR_PERF || SMP) && !HAVE_NMI_WATCHDOG
- default y
-
-# This will select the appropriate non-arch hardlockdup detector
-config HARDLOCKUP_DETECTOR_NON_ARCH
- bool
- depends on HAVE_HARDLOCKUP_DETECTOR_NON_ARCH
- select HARDLOCKUP_DETECTOR_BUDDY if !HAVE_HARDLOCKUP_DETECTOR_PERF || HARDLOCKUP_DETECTOR_PREFER_BUDDY
- select HARDLOCKUP_DETECTOR_PERF if HAVE_HARDLOCKUP_DETECTOR_PERF && !HARDLOCKUP_DETECTOR_PREFER_BUDDY
-
#
# Enables a timestamp based low pass filter to compensate for perf based
# hard lockup detection which runs too fast due to turbo modes.