rcu self-detected stall messages on OMAP3, 4 boards
Paul E. McKenney
paulmck at linux.vnet.ibm.com
Mon Sep 24 18:00:23 EDT 2012
On Mon, Sep 24, 2012 at 09:54:00PM +0000, Paul Walmsley wrote:
> On Sat, 22 Sep 2012, Paul E. McKenney wrote:
>
> > On Sat, Sep 22, 2012 at 10:20:19PM +0000, Paul Walmsley wrote:
> > > On Sat, 22 Sep 2012, Paul E. McKenney wrote:
> > >
> > > > This thing has been in the kernel since about 2004, not sure why you
> > > > didn't hit it earlier.
> > >
> > > One other data point in that regard - noticed the warnings don't appear
> > > when the board is booted with:
> > >
> > > commit 4fa3b6cb1bc8c14b81b4c8ffdfd3f2500a7e9367
> > > Author: Paul E. McKenney <paul.mckenney at linaro.org>
> > > Date: Tue Jun 5 15:53:53 2012 -0700
> > >
> > > rcu: Fix qlen_lazy breakage
> >
> > You lost me on this one. This is already in mainline, so if you were
> > using (say) 3.6-rc6, you would already have this commit applied.
>
> If I check out a kernel at this commit
> 4fa3b6cb1bc8c14b81b4c8ffdfd3f2500a7e9367 + the
> zero-callback-in-tickless-idle diagnostic patch, build and boot it, then
> the stall warnings don't appear (in 25 minutes of testing).
>
> Messages from the diagnostic patch indicate that the kernel is entering
> idle during a grace period with no RCU callbacks, though.
>
> This is not a big deal and does not need any further attention. Just
> wanted to place a time boundary on the point when these messages started
> appearing. (It is unlikely to be an optimal bound: i.e., there are
> probably later commits where the warnings also don't appear.)
Ah, got it, thank you!
Thanx, Paul
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