Re: [RFC PATCH 1/2] rcu: sysctl: Panic on RCU Stall

Josh Triplett
2016-05-31T19:18:40Z

On Tue, May 31, 2016 at 04:07:32PM -0300, Daniel Bristot de Oliveira wrote:
> It is not always easy to define the cause of an RCU stall just by
> analysing the RCU stall messages, mainly when the problem is caused
> by the indirect starvation of rcu threads. For example, when preempt_rcu
> is not awakened due to the starvation of a timer softirq.
>
> We have been hard coding panic() in the RCU stall functions for
> some time while testing the kernel-rt. But this is not possible in
> some scenarios, like when supporting customers.
>
> This patch implements the sysctl kerner.panic_on_rcu_stall. If
> set to 1, the system will panic() when an RCU stall takes place,
> enabling the capture of a vmcore. The vmcore provides a way to analyze
> all kernel/tasks states, helping out to point to the culprit and the
> solution for the stall.
>
> The kerner.panic_on_rcu_stall sysctl is disabled by default.

s/kerner/kernel/ (here and in the previous paragraph).

Also, even though it's only two lines, please consider creating a static
function wrapping the if and panic, to avoid duplication.

With those changes,
Reviewed-by: Josh Triplett <josh@joshtriplett.org>