On Fri, May 10, 2019 at 02:47:49PM -0400, Steven Rostedt wrote: > > As nobody else commented, I will ;) > > Hi Zhenzhong! > > On Sun, 14 Apr 2019 11:11:04 +0800 > Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx> wrote: > > > As stated in "Documentation/lockup-watchdogs.txt:line 22", the default > > behaivor after 'hardlockup' is to stay locked up rather than panic. > > That actually says: > > A 'hardlockup' is defined as a bug that causes the CPU to loop in > kernel mode for more than 10 seconds (see "Implementation" below for > details), without letting other interrupts have a chance to run. > Similarly to the softlockup case, the current stack trace is displayed > upon detection and the system will stay locked up unless the default > behavior is changed, which can be done through a sysctl, > 'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC", > and a kernel parameter, "nmi_watchdog" > > If your config has: > > CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y > > The kernel will panic on hard lockup by default unless you add nopanic. > > If your config has: > > # CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is not set > > Then the default will be not to panic unless you add "panic" to the > kernel command line. > > > > > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx> > > --- > > Documentation/admin-guide/kernel-parameters.txt | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 2b8ee90..fcc9579 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2769,7 +2769,7 @@ > > 0 - turn hardlockup detector in nmi_watchdog off > > 1 - turn hardlockup detector in nmi_watchdog on > > When panic is specified, panic when an NMI watchdog > > - timeout occurs (or 'nopanic' to override the opposite > > + timeout occurs (or 'nopanic' which is the opposite > > default). To disable both hard and soft lockup detectors, > > Honestly, I think the original text states what it does better than > your update. Because the nopanic is added to override the "opposite > default" which is if the config was set to do so. > > That said, this all still can be explained better. What about: > > nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels > Format: [panic,][nopanic,][num] > Valid num: 0 or 1 > 0 - turn hardlockup detector in nmi_watchdog off > 1 - turn hardlockup detector in nmi_watchdog on > When panic is specified, panic when an NMI watchdog > timeout occurs (or 'nopanic' to not panic on an NMI > watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set) > To disable both hard and soft lockup detectors, > please see 'nowatchdog'. > This is useful when you use a panic=... timeout and > need the box quickly up again. Steven, your update makes it more clear to me. If patch is being written with such update, here is my Reviewed-by: Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> thanks! - Joel > > -- Steve > > > > please see 'nowatchdog'. > > This is useful when you use a panic=... timeout and >
