Messages in this thread | | | Date | Thu, 9 Jun 2022 20:41:35 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu/tree: Add comment to describe GP done condition in fqs loop |
| |
On Fri, Jun 10, 2022 at 08:45:42AM +0530, Neeraj Upadhyay wrote: > > > On 6/10/2022 1:53 AM, Paul E. McKenney wrote: > > On Thu, Jun 09, 2022 at 12:43:40PM +0530, Neeraj Upadhyay wrote: > > > Add a comment to explain why !rcu_preempt_blocked_readers_cgp() condition > > > is required on root rnp node, for GP completion check in rcu_gp_fqs_loop(). > > > > > > Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> > > > > Thank you, Neeraj! As usual, I could not resist the urge to wordsmith > > as shown below. Could you please check to see if I messed something up? > > Thanks! > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit bdf3a744d3ad21336a390bfcc2e41de63f193eaf > > Author: Neeraj Upadhyay <quic_neeraju@quicinc.com> > > Date: Thu Jun 9 12:43:40 2022 +0530 > > > > rcu/tree: Add comment to describe GP-done condition in fqs loop > > Add a comment to explain why !rcu_preempt_blocked_readers_cgp() condition > > is required on root rnp node, for GP completion check in rcu_gp_fqs_loop(). > > Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index a93c5f4d7e092..9a941e7ee6109 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -2083,7 +2083,15 @@ static noinline_for_stack void rcu_gp_fqs_loop(void) > > rcu_gp_torture_wait(); > > WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS); > > /* Locking provides needed memory barriers. */ > > - /* If grace period done, leave loop. */ > > + /* > > + * Exit the loop if the root rcu_node structure indicates that the grace period > > + * has ended, leave the loop. The rcu_preempt_blocked_readers_cgp(rnp) check > > We can remove ", leave the loop" ? > > > + * is required only for single-node rcu_node trees because readers blocking > > + * the current grace period are queued only on leaf rcu_node structures. > > + * For multi-node trees, checking the root node's ->qsmask suffices, because a > > + * given root node's ->qsmask bit is cleared only when all CPUs and tasks from > > Do we need to say "a given root node's" , we have only single RCU node in > the system, so we can just say, "because root node's ->qsmask bit is > cleared..." ? > > > + * the corresponding leaf node have passed through their quiescent state. > > Change "the corresponding leaf node" to "their corresponding leaf nodes" or > "the corresponding leaf nodes"?
And the winner is "the corresponding leaf nodes"! Good catch, and thank you!
Thanx, Paul
> Thanks > Neeraj > > > + */ > > if (!READ_ONCE(rnp->qsmask) && > > !rcu_preempt_blocked_readers_cgp(rnp)) > > break;
| |