path: root/kernel/sysctl.c
diff options
authorAaron Tomlin <>2014-06-23 13:22:05 -0700
committerLinus Torvalds <>2014-06-23 16:47:44 -0700
commited235875e2ca983197831337a986f0517074e1a0 (patch)
treea562c7ac13452a0573b87977df7b26a6471ece38 /kernel/sysctl.c
parentf3aca3d09525f87731ba6b892c9b010570bc54b4 (diff)
kernel/watchdog.c: print traces for all cpus on lockup detection
A 'softlockup' is defined as a bug that causes the kernel to loop in kernel mode for more than a predefined period to time, without giving other tasks a chance to run. Currently, upon detection of this condition by the per-cpu watchdog task, debug information (including a stack trace) is sent to the system log. On some occasions, we have observed that the "victim" rather than the actual "culprit" (i.e. the owner/holder of the contended resource) is reported to the user. Often this information has proven to be insufficient to assist debugging efforts. To avoid loss of useful debug information, for architectures which support NMI, this patch makes it possible to improve soft lockup reporting. This is accomplished by issuing an NMI to each cpu to obtain a stack trace. If NMI is not supported we just revert back to the old method. A sysctl and boot-time parameter is available to toggle this feature. [ add CONFIG_SMP in certain areas] [ additional CONFIG_SMP=n optimisations] [ fix warning] Signed-off-by: Aaron Tomlin <> Signed-off-by: Don Zickus <> Cc: David S. Miller <> Cc: Mateusz Guzik <> Cc: Oleg Nesterov <> Signed-off-by: Jan Moskyto Matejka <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/sysctl.c')
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 075d1903138f..75b22e22a72c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -860,6 +860,17 @@ static struct ctl_table kern_table[] = {
.extra1 = &zero,
.extra2 = &one,
+#ifdef CONFIG_SMP
+ {
+ .procname = "softlockup_all_cpu_backtrace",
+ .data = &sysctl_softlockup_all_cpu_backtrace,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one,
+ },
+#endif /* CONFIG_SMP */
.procname = "nmi_watchdog",
.data = &watchdog_user_enabled,