watchdog/hardlockup: keep kernel.nmi_watchdog sysctl as 0444 if probe fails

Patch series "watchdog: Cleanup / fixes after buddy series v5 reviews".

This patch series attempts to finish resolving the feedback received
from Petr Mladek on the v5 series I posted.

Probably the only thing that wasn't fully as clean as Petr requested was
the Kconfig stuff.  I couldn't find a better way to express it without a
more major overhaul.  In the very least, I renamed "NON_ARCH" to
"PERF_OR_BUDDY" in the hopes that will make it marginally better.

Nothing in this series is terribly critical and even the bugfixes are
small.  However, it does cleanup a few things that were pointed out in
review.

This patch (of 10):

The permissions for the kernel.nmi_watchdog sysctl have always been set at
compile time despite the fact that a watchdog can fail to probe.  Let's
fix this and set the permissions based on whether the hardlockup detector
actually probed.

Link: https://lkml.kernel.org/r/20230527014153.2793931-1-dianders@chromium.org
Link: https://lkml.kernel.org/r/20230526184139.1.I0d75971cc52a7283f495aac0bd5c3041aadc734e@changeid
Fixes: a994a3147e4c ("watchdog/hardlockup/perf: Implement init time detection of perf")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reported-by: Petr Mladek <pmladek@suse.com>
Closes: https://lore.kernel.org/r/ZHCn4hNxFpY5-9Ki@alley
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/include/linux/nmi.h b/include/linux/nmi.h
index 83577ae..99b7d74 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -95,12 +95,6 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs);
 static inline void arch_touch_nmi_watchdog(void) { }
 #endif
 
-#if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR)
-# define NMI_WATCHDOG_SYSCTL_PERM      0644
-#else
-# define NMI_WATCHDOG_SYSCTL_PERM      0444
-#endif
-
 #if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
 extern void hardlockup_detector_perf_stop(void);
 extern void hardlockup_detector_perf_restart(void);

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 237990e..4b9e31e 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -881,15 +881,6 @@ static struct ctl_table watchdog_sysctls[] = {
                .extra2         = (void *)&sixty,
        },
        {
-               .procname       = "nmi_watchdog",
-               .data           = &watchdog_hardlockup_user_enabled,
-               .maxlen         = sizeof(int),
-               .mode           = NMI_WATCHDOG_SYSCTL_PERM,
-               .proc_handler   = proc_nmi_watchdog,
-               .extra1         = SYSCTL_ZERO,
-               .extra2         = SYSCTL_ONE,
-       },
-       {
                .procname       = "watchdog_cpumask",
                .data           = &watchdog_cpumask_bits,
                .maxlen         = NR_CPUS,
@@ -952,10 +943,28 @@ static struct ctl_table watchdog_sysctls[] = {
        {}
 };
 
+static struct ctl_table watchdog_hardlockup_sysctl[] = {
+       {
+               .procname       = "nmi_watchdog",
+               .data           = &watchdog_hardlockup_user_enabled,
+               .maxlen         = sizeof(int),
+               .mode           = 0444,
+               .proc_handler   = proc_nmi_watchdog,
+               .extra1         = SYSCTL_ZERO,
+               .extra2         = SYSCTL_ONE,
+       },
+       {}
+};
+
 static void __init watchdog_sysctl_init(void)
 {
        register_sysctl_init("kernel", watchdog_sysctls);
+
+       if (watchdog_hardlockup_available)
+               watchdog_hardlockup_sysctl[0].mode = 0644;
+       register_sysctl_init("kernel", watchdog_hardlockup_sysctl);
 }
+
 #else
 #define watchdog_sysctl_init() do { } while (0)
 #endif /* CONFIG_SYSCTL */
@@ -1011,6 +1020,8 @@ static int __init lockup_detector_check(void)
        /* Make sure no work is pending. */
        flush_work(&detector_work);
 
+       watchdog_sysctl_init();
+
        return 0;
 
 }
@@ -1030,5 +1041,4 @@ void __init lockup_detector_init(void)
                allow_lockup_detector_init_retry = true;
 
        lockup_detector_setup();
-       watchdog_sysctl_init();
 }