Re: automount hangs during boot somewhere in rcu_barrier.

From: Gleb Natapov
Date: Tue Jun 05 2012 - 05:47:01 EST


On Mon, Jun 04, 2012 at 07:54:32AM -0700, Paul E. McKenney wrote:
> On Mon, Jun 04, 2012 at 01:09:25PM +0300, Gleb Natapov wrote:
> > On Mon, Jun 04, 2012 at 10:48:03AM +0300, Gleb Natapov wrote:
> > > On Sun, Jun 03, 2012 at 08:15:49PM -0700, Paul E. McKenney wrote:
> > > > Hmmm... Could you please try disabling CONFIG_RCU_FAST_NO_HZ? If that
> > > > makes the problem go away, I have some patches 3.6-targeted patches
> > > > for you.
> > > Will report back.
> > >
> > Do not see any problems with the option disabled.
>
> OK, then you are probably being bitten by the same bug that was biting
> Pascal and Heiko. Could you please apply the following series from -rcu?
>
> bf7757c3 (Merge commit 'v3.4-rc6' into HEAD)
> edc17350 (RCU_FAST_NO_HZ detection of callback adoption)
> 8e03a88e (Update RCU_FAST_NO_HZ tracing for lazy callbacks)
> f2298c63 (Move RCU_FAST_NO_HZ per-CPU variables to rcu_dynticks structure)
> 05cc0fc9 (Precompute RCU_FAST_NO_HZ timer offsets)
> 477fca01 (Dump only the current CPU's buffers for idle-entry/exit warnings)
> f29075fb (The rcu_needs_cpu() function is not a quiescent state)
>
> Of these, 05cc0fc9 (Precompute RCU_FAST_NO_HZ timer offsets) is likely
> to be the most relevant. The -rcu tree may be found at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>
> Please let me know if you have any trouble pulling this series.
>
The problem is gone with the series + enabling CONFIG_RCU_FAST_NO_HZ
back.

--
Gleb.
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