watchdog/hardlockup: HAVE_NMI_WATCHDOG must implement watchdog_hardlockup_probe()

Right now there is one arch (sparc64) that selects HAVE_NMI_WATCHDOG
without selecting HAVE_HARDLOCKUP_DETECTOR_ARCH.  Because of that one
architecture, we have some special case code in the watchdog core to
handle the fact that watchdog_hardlockup_probe() isn't implemented.

Let's implement watchdog_hardlockup_probe() for sparc64 and get rid of the
special case.

As a side effect of doing this, code inspection tells us that we could fix
a minor bug where the system won't properly realize that NMI watchdogs are
disabled.  Specifically, on powerpc if CONFIG_PPC_WATCHDOG is turned off
the arch might still select CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH which
selects CONFIG_HAVE_NMI_WATCHDOG.  Since CONFIG_PPC_WATCHDOG was off then
nothing will override the "weak" watchdog_hardlockup_probe() and we'll
fallback to looking at CONFIG_HAVE_NMI_WATCHDOG.

Link: https://lkml.kernel.org/r/20230526184139.2.Ic6ebbf307ca0efe91f08ce2c1eb4a037ba6b0700@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
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>

diff --git a/arch/Kconfig b/arch/Kconfig
index 205fd23..422f0ff 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -405,7 +405,8 @@ config HAVE_NMI_WATCHDOG
        bool
        help
          The arch provides a low level NMI watchdog. It provides
-         asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
+         asm/nmi.h, and defines its own watchdog_hardlockup_probe() and
+         arch_touch_nmi_watchdog().
 
 config HAVE_HARDLOCKUP_DETECTOR_ARCH
        bool

diff --git a/arch/sparc/kernel/nmi.c b/arch/sparc/kernel/nmi.c
index 9d9e29b..17cdfdb 100644 (file)
--- a/arch/sparc/kernel/nmi.c
+++ b/arch/sparc/kernel/nmi.c
@@ -65,6 +65,11 @@ void arch_touch_nmi_watchdog(void)
 }
 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 
+int __init watchdog_hardlockup_probe(void)
+{
+       return 0;
+}
+
 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
 {
        int this_cpu = smp_processor_id();

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 4b9e31e..62230f5 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -217,19 +217,6 @@ void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
  */
 int __weak __init watchdog_hardlockup_probe(void)
 {
-       /*
-        * If CONFIG_HAVE_NMI_WATCHDOG is defined then an architecture
-        * is assumed to have the hard watchdog available and we return 0.
-        */
-       if (IS_ENABLED(CONFIG_HAVE_NMI_WATCHDOG))
-               return 0;
-
-       /*
-        * Hardlockup detectors other than those using CONFIG_HAVE_NMI_WATCHDOG
-        * are required to implement a non-weak version of this probe function
-        * to tell whether they are available. If they don't override then
-        * we'll return -ENODEV.
-        */
        return -ENODEV;
 }