Re: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stallwarnings

[Steven Rostedt]

On Thu, 2012-09-06 at 16:56 +0200, Peter Zijlstra wrote:
> On Thu, 2012-08-30 at 11:56 -0700, Paul E. McKenney wrote:
> > 
> > If a given CPU avoids the idle loop but also avoids starting a new
> > RCU grace period for a full minute, RCU can issue spurious RCU CPU
> > stall warnings.  This commit fixes this issue by adding a check for
> > ongoing grace period to avoid these spurious stall warnings. 
> 
> How would it avoid starting a new period for over a minute? fqs should
> happen, right? And holding rcu_read_lock() for over a minute surely is a
> bug.

I can see this happening in test cases, but it would seem weird on a
normal system. That is, for preempt rcu, having a process scheduled out
holding an rcu_read_lock() for over a minute could happen on a really
stressed out system. But for such a case, I don't think a warning is out
of question.

-- Steve


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/