Re: [PATCH]: Fix bogus softlockup warning with sysrq-t

[Jeremy Fitzhardinge <jeremy@goop.org>]

Prarit Bhargava wrote:
> There are some situations when soft lockup warnings are expected in the
> kernel.  For example, when doing an alt-sysrq-t on a large number of processes,
> the dump to console can take a long time and the tasklist_lock is held over
> that period.  This results in a bogus soft lockup warning.
>   

Wouldn't it be better to just temporarily disable softlockups for the
duration?

> This patch reworks touch_softlockup_watchdog to touch ALL cpu's
> touch_timestamp.  It also introduces touch_cpu_softlockup_watchdog to touch
> a single cpu's touch_timestamp.

Doesn't this mean that if one CPU gets locked up, it will be undetected
so long as some other CPU is making progress?

I have another pair of softlockup patches in which I try to address:

    * ignoring time stolen by hypervisors
    * threads going to sleep tickless for long periods of time

I could easy add a "global disable" function, which would allow long
sysrq messages, and it would help Thilo with his long flash update freezes.

    J