Re: [PATCH] rcu: tree_stall: Correctly unlock root node in rcu_check_gp_start_stall

[Neeraj Upadhyay]

On 3/30/19 2:57 AM, Paul E. McKenney wrote:
> On Fri, Mar 29, 2019 at 07:52:15PM +0530, Neeraj Upadhyay wrote:
> > On 3/29/19 6:58 PM, Mukesh Ojha wrote:
> > > On 3/29/2019 4:57 PM, Neeraj Upadhyay wrote:
> > > > Only unlock the root node, if current node (rnp) is not
> > > > root node.
> > > >
> > > > Signed-off-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
> > >
> > >
> > >
> > > > ---
> > > >  Â kernel/rcu/tree_stall.h | 4 +++-
> > > >  Â 1 file changed, 3 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> > > > index f65a73a..0651833 100644
> > > > --- a/kernel/rcu/tree_stall.h
> > > > +++ b/kernel/rcu/tree_stall.h
> > >
> > >
> > > why this is showing as under tree_stall.h while it is under
> > > "kernel/rcu/tree.c"
> >
> > It's moved in https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=dev&id=10462d6f58fb6dbde7563e9343505d98d5bfba3d
> >
> > Please see linux-rcu dev tree for other changes, which moves code to
> > this file.
> >
> >
> > Thanks
> > Neeraj
> >
> > > > @@ -630,7 +630,9 @@ static void rcu_check_gp_start_stall(struct
> > > > rcu_node *rnp, struct rcu_data *rdp,
> > > >  ÂÂÂÂÂÂÂÂÂ time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
> > > >  ÂÂÂÂÂÂÂÂÂ time_before(j, rcu_state.gp_activity + gpssdelay) ||
> > > >  ÂÂÂÂÂÂÂÂÂ atomic_xchg(&warned, 1)) {
> > > > -ÂÂÂÂÂÂÂ raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
> > > > +ÂÂÂÂÂÂÂ if (rnp_root != rnp)
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ /* irqs remain disabled. */
> > > > +ÂÂÂÂÂÂÂÂÂÂÂ raw_spin_unlock_rcu_node(rnp_root);
> > >
> > > Looks good as it will balance the lock .if it is the root_node,
> > > which was not there earlier, and unlock was happening without any
> > > lock on root.
> > >
> > > Reviewed-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
>
> Applied, again thank you both!
>
> In both cases, I updated the commit log, so please check to make sure
> that I didn't mess anything up.
>
> 							Thanx, Paul

Thanks Paul. One minor comment on 
https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=dev&id=ec6530e763046b6bb1f4c2c2aed49ebc68aae2a0 


"it clearly does not make sense to release
both rnp->lock and rnp->lock"

should be rnp->lock and rnp_root->lock



Thanks
Neeraj

> > > Cheers,
> > > -Mukesh
> > >
> > > >  ÂÂÂÂÂÂÂÂÂ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> > > >  ÂÂÂÂÂÂÂÂÂ return;
> > > >  ÂÂÂÂÂ }
> >
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> > member of the Code Aurora Forum, hosted by The Linux Foundation

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation