Messages in this thread | | | Date | Thu, 28 Feb 2008 10:35:08 +0530 | From | Gautham R Shenoy <> | Subject | Re: [PATCH] Fix hibernate/resume in presence of PREEMPT_RCU and hotplug |
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On Wed, Feb 27, 2008 at 04:21:10PM -0800, Paul E. McKenney wrote: > Hello! > > This fixes a oops encountered when doing hibernate/resume in presence > of PREEMPT_RCU. The problem was that the code failed to disable preemption > when accessing a per-CPU variable. This is OK when called from code > that already has preemption disabled, but such is not the case from > the suspend/resume code path.
Well, rcu_offline_cpu() is called from the cpu-offline callback path, and AFAICS, it doesn't disable preemption.
I wonder how we're seeing this only now! Indeed a good catch!
Reviewed-by: Gautham R Shenoy <ego@in.ibm.com>
> > Reported-by: Dave Young <hidave.darkstar@gmail.com> > Tested-by: Dave Young <hidave.darkstar@gmail.com> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > > rcupreempt.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff -urpNa -X dontdiff linux-2.6.25-rc3/kernel/rcupreempt.c linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c > --- linux-2.6.25-rc3/kernel/rcupreempt.c 2008-02-26 16:58:43.000000000 -0800 > +++ linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c 2008-02-26 17:04:17.000000000 -0800 > @@ -702,8 +702,9 @@ void rcu_offline_cpu(int cpu) > * fix. > */ > > + local_irq_save(flags); > rdp = RCU_DATA_ME(); > - spin_lock_irqsave(&rdp->lock, flags); > + spin_lock(&rdp->lock); > *rdp->nexttail = list; > if (list) > rdp->nexttail = tail;
-- Thanks and Regards gautham
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