watchdog/sysctl: Get rid of the #ifdeffery

The sysctl of the nmi_watchdog file prevents writes by setting:

    min = max = 0

if none of the users is enabled. That involves ifdeffery and is competely
non obvious.

If none of the facilities is enabeld, then the file can simply be made read
only. Move the ifdeffery into the header and use a constant for file
permissions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194147.706073616@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index cfebb3b..5774b44 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -81,6 +81,12 @@ extern unsigned int hardlockup_panic;
 static inline void hardlockup_detector_disable(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 arch_touch_nmi_watchdog(void);
 extern void hardlockup_detector_perf_stop(void);

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6648fbb..539cb4e 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -891,14 +891,10 @@ static struct ctl_table kern_table[] = {
                .procname       = "nmi_watchdog",
                .data           = &nmi_watchdog_enabled,
                .maxlen         = sizeof (int),
-               .mode           = 0644,
+               .mode           = NMI_WATCHDOG_SYSCTL_PERM,
                .proc_handler   = proc_nmi_watchdog,
                .extra1         = &zero,
-#if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR)
                .extra2         = &one,
-#else
-               .extra2         = &zero,
-#endif
        },
        {
                .procname       = "watchdog_cpumask",