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

[Neeraj Upadhyay]

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>
>
> Cheers,
> -Mukesh
>
> > ÂÂÂÂÂÂÂÂÂ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> > ÂÂÂÂÂÂÂÂÂ return;
> > ÂÂÂÂÂ }

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