Messages in this thread | | | Date | Thu, 28 Feb 2008 11:43:23 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] Fix hibernate/resume in presence of PREEMPT_RCU and hotplug |
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On Thu, Feb 28, 2008 at 10:35:08AM +0530, Gautham R Shenoy wrote: > 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!
I wonder as well. In fact there is (at least) one other such bug, submitting patch separately. :-/
Thanx, Paul
> 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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