Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-22 Thread Paul E. McKenney
On Mon, May 21, 2018 at 09:43:27PM -0700, Joel Fernandes wrote: > On Mon, May 21, 2018 at 09:16:51PM -0700, Paul E. McKenney wrote: > > On Mon, May 21, 2018 at 05:28:23PM -0700, Paul E. McKenney wrote: > > > On Mon, May 21, 2018 at 05:07:34PM -0700, Joel Fernandes wrote: > > > > On Mon, May 21, 201

Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-21 Thread Joel Fernandes
On Mon, May 21, 2018 at 09:16:51PM -0700, Paul E. McKenney wrote: > On Mon, May 21, 2018 at 05:28:23PM -0700, Paul E. McKenney wrote: > > On Mon, May 21, 2018 at 05:07:34PM -0700, Joel Fernandes wrote: > > > On Mon, May 21, 2018 at 04:25:38PM -0700, Paul E. McKenney wrote: > > > > On Sun, May 20, 2

Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-21 Thread Paul E. McKenney
On Mon, May 21, 2018 at 05:28:23PM -0700, Paul E. McKenney wrote: > On Mon, May 21, 2018 at 05:07:34PM -0700, Joel Fernandes wrote: > > On Mon, May 21, 2018 at 04:25:38PM -0700, Paul E. McKenney wrote: > > > On Sun, May 20, 2018 at 09:42:20PM -0700, Joel Fernandes wrote: > > > > We acquire gp_seq_n

Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-21 Thread Paul E. McKenney
On Mon, May 21, 2018 at 05:07:34PM -0700, Joel Fernandes wrote: > On Mon, May 21, 2018 at 04:25:38PM -0700, Paul E. McKenney wrote: > > On Sun, May 20, 2018 at 09:42:20PM -0700, Joel Fernandes wrote: > > > We acquire gp_seq_needed locklessly. To be safe, lets do the unlocking > > > after the access

Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-21 Thread Joel Fernandes
On Mon, May 21, 2018 at 04:25:38PM -0700, Paul E. McKenney wrote: > On Sun, May 20, 2018 at 09:42:20PM -0700, Joel Fernandes wrote: > > We acquire gp_seq_needed locklessly. To be safe, lets do the unlocking > > after the access. > > Actually, no, we hold rnp_start's ->lock throughout. And this CP

Re: [PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-21 Thread Paul E. McKenney
On Sun, May 20, 2018 at 09:42:20PM -0700, Joel Fernandes wrote: > We acquire gp_seq_needed locklessly. To be safe, lets do the unlocking > after the access. Actually, no, we hold rnp_start's ->lock throughout. And this CPU (or in the case of no-CBs CPUs, this task) is in charge of rdp->gp_seq_nee

[PATCH v3 4/4] rcu: Unlock non-start node only after accessing its gp_seq_needed

2018-05-20 Thread Joel Fernandes
We acquire gp_seq_needed locklessly. To be safe, lets do the unlocking after the access. Signed-off-by: Joel Fernandes --- kernel/rcu/tree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 879c67a31116..efbd21b2a1a6 100644 --- a