On Sun, Apr 21, 2013 at 08:10:35PM +0200, Borislav Petkov wrote:
> On Sun, Apr 21, 2013 at 06:56:54PM +0200, Borislav Petkov wrote:
> > Ok, let me try to disable the soundcard in the BIOS.
>
> Ok, there's no warning message anymore but maybe a dozen of seconds
> delay before the machine is actually powered off.
That is not so good...
> "...
> ACPI: Preparing to enter system sleep state S5
> [Firmware Bug]: ACPI: BIOS _OSI(Linux) query ignored
> <a bunch of seconds of doing nothing>
> ...
> <machine powers off>"
>
> So could it be that some RCU cleanup stuff is going on during that time?
CONFIG_RCU_FAST_NO_HZ will definitely change the timing, for example,
increasing grace-period durations by up to a factor of four.
One way to figure out if this is the problem would be to either (1) apply
the following patch (assuming you have no more than a few tens of CPUs)
or (2) setting the sysfs rcutree.rcu_expedited variable to 1 just before
suspending the system.
Either approach will force RCU to always use the faster expedited
grace periods for synchronize_rcu() and friends. They will -not- help
if someone has open-coded synchronize_rcu() in terms of call_rcu(),
though.
> I mean, the issue is not that big of a deal - when the box resumes, the
> sound card works just fine so...
Fair point. perhaps we should wait for Takashi to weigh in.
Thanx, Paul
> Thanks.
>
> --
> Regards/Gruss,
> Boris.
>
> Sent from a fat crate under my desk. Formatting is fine.
> --
------------------------------------------------------------------------
rcu: Not for inclusion: Force expedited grace periods
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index a9610d1..55c5ef6 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -2420,7 +2420,7 @@ void synchronize_sched(void)
"Illegal synchronize_sched() in RCU-sched read-side
critical section");
if (rcu_blocking_is_gp())
return;
- if (rcu_expedited)
+ if (1)
synchronize_sched_expedited();
else
wait_rcu_gp(call_rcu_sched);
@@ -2447,7 +2447,7 @@ void synchronize_rcu_bh(void)
"Illegal synchronize_rcu_bh() in RCU-bh read-side
critical section");
if (rcu_blocking_is_gp())
return;
- if (rcu_expedited)
+ if (1)
synchronize_rcu_bh_expedited();
else
wait_rcu_gp(call_rcu_bh);
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 46b93b0..190a199 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -711,7 +711,7 @@ void synchronize_rcu(void)
"Illegal synchronize_rcu() in RCU read-side critical
section");
if (!rcu_scheduler_active)
return;
- if (rcu_expedited)
+ if (1)
synchronize_rcu_expedited();
else
wait_rcu_gp(call_rcu);
--
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