Re: REGRESSION: 3.10-rc1: Dell Latitude e6410 hangs within 3 seconds

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Fri, May 17, 2013 at 10:49:16PM +0200, Arend van Spriel wrote:
> On 05/14/2013 10:38 PM, Arend van Spriel wrote:
> >On 05/14/2013 10:34 PM, Rafael J. Wysocki wrote:
> >>On Tuesday, May 14, 2013 03:03:58 PM Arend van Spriel wrote:
> >>>Laptop hangs pretty soon after booting. Workaround for me was to turn
> >>>off ACPI on kernel command line, ie. acpi=off
> >>>
> >>>Attached is my kernel configuration.
> >>
> >>Well, I have no idea what may be the source of this.
> >
> >Me neither.
> >
> >>Any chance to bisect?
> >
> >can try. Rebuilding kernels can be a drag :-p
> >
> >Regards,
> >Arend
> 
> Hi Rafael,
> 
> The bisect result found commit c0f4dfd4f as culprit. I also verified
> that the merge into Linus' tree introduced the issue upstream, ie.
> 6c24499 works and 1f889ec does not. I tried to revert the commit,
> but that was a bit risky (conflict to resolve) and did not give me a
> stable kernel. The only thing that works is selecting acpi=off. I
> tried also nohz=off but that resulted in /init failure.
> 
> Regards,
> Arend
> 
> ---8<----------------------------------------------------------------
> 
> commit 1f889ec62c3f0d8913f3c32f9aff2a1e15099346
>   Merge: 6c24499 8fcfae3
> 
>   commit 8fcfae31719c0a6c03f2cf63f815b46d378d8be4
>     Merge: d02a9a8 6d87669
> 
>     commit 6d87669357936bffa1e8fea7a4e7743e76905736
>       Merge: 3f944ad 81e5949 910ee45
> 
>       commit c0f4dfd4f90f1667d234d21f15153ea09a2eaa66
>       Author: Paul E. McKenney <paul.mckenney@linaro.org>
>       Date:   Fri Dec 28 11:30:36 2012 -0800
> 
>           rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks
> 
>           Because RCU callbacks are now associated with the number
>           of the grace period that they must wait for, CPUs can now
>           take advance callbacks corresponding to grace periods that
>           ended while a given CPU was in dyntick-idle mode. This
>           eliminates the need to try forcing the RCU state machine
>           while entering idle, thus reducing the CPU intensiveness
>           of RCU_FAST_NO_HZ, which should increase its energy
>           efficiency.
> 
>       Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
>       Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Hello, Arend,

Thank you for tracking this down!  Could you please try out the following
patch?

							Thanx, Paul

------------------------------------------------------------------------

rcu: Fix comparison sense in rcu_needs_cpu()

Commit c0f4dfd4f (rcu: Make RCU_FAST_NO_HZ take advantage of numbered
callbacks) introduced a bug that can result in excessively long grace
periods.  This bug reverse the senes of the "if" statement checking
for lazy callbacks, so that RCU takes a lazy approach when there are
in fact non-lazy callbacks.  This can result in excessive boot, suspend,
and resume times.

This commit therefore fixes the sense of this "if" statement.

Reported-by: Borislav Petkov <bp@alien8.de>
Reported-by: Bjørn Mork <bjorn@mork.no>
Reported-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Bjørn Mork <bjorn@mork.no>
Tested-by: Joerg Roedel <joro@8bytes.org>

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 170814d..6d939a6 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1667,7 +1667,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj)
 	rdtp->last_accelerate = jiffies;
 
 	/* Request timer delay depending on laziness, and round. */
-	if (rdtp->all_lazy) {
+	if (!rdtp->all_lazy) {
 		*dj = round_up(rcu_idle_gp_delay + jiffies,
 			       rcu_idle_gp_delay) - jiffies;
 	} else {

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