Re: RCU stall and the system boot hang

From: Paul E. McKenney
Date: Tue Dec 01 2015 - 14:55:04 EST


On Mon, Nov 30, 2015 at 09:19:18AM -0800, Paul E. McKenney wrote:
> On Mon, Nov 30, 2015 at 02:54:13PM +0800, fupan li wrote:

[ . . . ]

> > No, just a normal boot, and these stalls were happened before
> > systemd services running.
>
> Interesting. My testing show v4.1 being OK, with the first issues showing
> up somewhere between v4.1 and v4.2. Or at least v4.1 is reliable enough
> that is passes 42 hours of focused rcutorture testing, where v4.2 tends
> to fail in under two hours. And it seems to happen only on multisocket
> systems -- I seem to be able to hammer as hard as I want on my four-core
> (eight hardware thread) laptop without an issue.

And I take it back. After beating on it for the better part of a week,
I did get one failure on my single-socket laptop.

So maybe I need to make my rcutorture scripts force tests to cross socket
boundaries where possible...

Thanx, Paul

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