softlockup: fix softlockup_thresh unaligned access and disable detection at runtime

Fix unaligned access errors when setting softlockup_thresh on
64 bit platforms.

Allow softlockup detection to be disabled by setting
softlockup_thresh <= 0.

Detect that boot time softlockup detection has been disabled
earlier in softlockup_tick.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2d3b388c402d..31c19a79738d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -84,12 +84,13 @@ extern int latencytop_enabled;
 extern int sysctl_nr_open_min, sysctl_nr_open_max;
 
 /* Constants used for minimum and  maximum */
-#if defined(CONFIG_DETECT_SOFTLOCKUP) || defined(CONFIG_HIGHMEM)
+#ifdef CONFIG_HIGHMEM
 static int one = 1;
 #endif
 
 #ifdef CONFIG_DETECT_SOFTLOCKUP
 static int sixty = 60;
+static int neg_one = -1;
 #endif
 
 #ifdef CONFIG_MMU
@@ -742,11 +743,11 @@ static struct ctl_table kern_table[] = {
                 .ctl_name       = CTL_UNNUMBERED,
                 .procname       = "softlockup_thresh",
                 .data           = &softlockup_thresh,
-                .maxlen         = sizeof(unsigned long),
+                .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = &proc_doulongvec_minmax,
+                .proc_handler   = &proc_dointvec_minmax,
                 .strategy       = &sysctl_intvec,
-                .extra1         = &one,
+                .extra1         = &neg_one,
                 .extra2         = &sixty,
         },
         {