[PATCH 3/7] watchdog/hardlockup: Declare arch_touch_nmi_watchdog() only in linux/nmi.h

Petr Mladek
2023-06-07T15:27:40Z

arch_touch_nmi_watchdog() needs a different implementation for various
hardlockup detector implementations. And it does nothing when
any hardlockup detector is not build at all.

arch_touch_nmi_watchdog() has to be declared in linux/nmi.h. It is done
directly in this header file for the perf and buddy detectors. And it
is done in the included asm/linux.h for arch specific detectors.

The reason probably is that the arch specific variants build the code
using another conditions. For example, powerpc64/sparc64 builds the code
when CONFIG_PPC_WATCHDOG is enabled.

Another reason might be that these architectures define more functions
in asm/nmi.h anyway.

However the generic code actually knows the information. The config
variables HAVE_NMI_WATCHDOG and HAVE_HARDLOCKUP_DETECTOR_ARCH are used
to decide whether to build the buddy detector.

In particular, CONFIG_HARDLOCKUP_DETECTOR is set only when a generic
or arch-specific hardlockup detector is built. The only exception
is sparc64 which ignores the global HARDLOCKUP_DETECTOR switch.

The information about sparc64 is a bit complicated. The hardlockup
detector is built there when CONFIG_HAVE_NMI_WATCHDOG is set and
CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH is not set.

People might wonder whether this change really makes things easier.
The motivation is:

+ The current logic in linux/nmi.h is far from obvious.
For example, arch_touch_nmi_watchdog() is defined as {} when
neither CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER nor
CONFIG_HAVE_NMI_WATCHDOG is defined.

+ The change synchronizes the checks in lib/Kconfig.debug and
in the generic code.

+ It is a step that will help cleaning HAVE_NMI_WATCHDOG related
checks.

The change should not change the existing behavior.

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
arch/powerpc/include/asm/nmi.h | 2 --
arch/sparc/include/asm/nmi.h | 1 -
include/linux/nmi.h | 13 ++++++++++---
3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
index 43bfd4de868f..ce25318c3902 100644
--- a/arch/powerpc/include/asm/nmi.h
+++ b/arch/powerpc/include/asm/nmi.h
@@ -3,11 +3,9 @@
#define _ASM_NMI_H

#ifdef CONFIG_PPC_WATCHDOG
-extern void arch_touch_nmi_watchdog(void);
long soft_nmi_interrupt(struct pt_regs *regs);
void watchdog_hardlockup_set_timeout_pct(u64 pct);
#else
-static inline void arch_touch_nmi_watchdog(void) {}
static inline void watchdog_hardlockup_set_timeout_pct(u64 pct) {}
#endif

diff --git a/arch/sparc/include/asm/nmi.h b/arch/sparc/include/asm/nmi.h
index 90ee7863d9fe..920dc23f443f 100644
--- a/arch/sparc/include/asm/nmi.h
+++ b/arch/sparc/include/asm/nmi.h
@@ -8,7 +8,6 @@ void nmi_adjust_hz(unsigned int new_hz);

extern atomic_t nmi_active;

-void arch_touch_nmi_watchdog(void);
void start_nmi_watchdog(void *unused);
void stop_nmi_watchdog(void *unused);

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index b5d0b7ab52fb..b9e816bde14a 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -7,6 +7,8 @@

#include <linux/sched.h>
#include <asm/irq.h>
+
+/* Arch specific watchdogs might need to share extra watchdog-related APIs. */
#if defined(CONFIG_HAVE_NMI_WATCHDOG)
#include <asm/nmi.h>
#endif
@@ -89,12 +91,17 @@ extern unsigned int hardlockup_panic;
static inline void hardlockup_detector_disable(void) {}
#endif

-#if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
+/* Sparc64 has special implemetantion that is always enabled. */
+#if defined(CONFIG_HARDLOCKUP_DETECTOR) || \
+ (defined(CONFIG_HAVE_NMI_WATCHDOG) && !defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH))
void arch_touch_nmi_watchdog(void);
+#else
+static inline void arch_touch_nmi_watchdog(void) { }
+#endif
+
+#if defined(CONFIG_HARDLOCKUP_DETECTOR_COUNTS_HRTIMER)
void watchdog_hardlockup_touch_cpu(unsigned int cpu);
void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs);
-#elif !defined(CONFIG_HAVE_NMI_WATCHDOG)
-static inline void arch_touch_nmi_watchdog(void) { }
#endif

#if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
--
2.35.3