On Thu, Jan 28, 2021 at 06:12:13PM +0100, Frederic Weisbecker wrote:
> Unconfuse a bit the name of this function which suggests returning true
> when the state is updated. It actually returns true when the rdp is in
> the process of deoffloading and we must ignore it.
>
> Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
> Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Fair point, thank you! I have queued this one for further review and
testing, with the usual wordsmithing shown below.
Thanx, Paul
------------------------------------------------------------------------
commit 142d159f544763140e0f498936bca8f71563e0e0
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
Date: Thu Jan 28 18:12:13 2021 +0100
rcu/nocb: Rename nocb_gp_update_state to nocb_gp_update_state_deoffloading
The name nocb_gp_update_state() is unenlightening, so this commit changes
it to nocb_gp_update_state_deoffloading(). This function now does what
its name says, updates state and returns true if the CPU corresponding to
the specified rcu_data structure is in the process of being de-offloaded.
Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index a3db700..9c0ee82 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2014,7 +2014,8 @@ static inline bool nocb_gp_enabled_cb(struct rcu_data *rdp)
return rcu_segcblist_test_flags(&rdp->cblist, flags);
}
-static inline bool nocb_gp_update_state(struct rcu_data *rdp, bool *needwake_state)
+static inline bool nocb_gp_update_state_deoffloading(struct rcu_data *rdp,
+ bool *needwake_state)
{
struct rcu_segcblist *cblist = &rdp->cblist;
@@ -2024,7 +2025,7 @@ static inline bool nocb_gp_update_state(struct rcu_data *rdp, bool *needwake_sta
if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
*needwake_state = true;
}
- return true;
+ return false;
}
/*
@@ -2035,7 +2036,7 @@ static inline bool nocb_gp_update_state(struct rcu_data *rdp, bool *needwake_sta
rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP);
if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
*needwake_state = true;
- return false;
+ return true;
}
@@ -2073,7 +2074,7 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
continue;
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
rcu_nocb_lock_irqsave(rdp, flags);
- if (!nocb_gp_update_state(rdp, &needwake_state)) {
+ if (nocb_gp_update_state_deoffloading(rdp, &needwake_state)) {
rcu_nocb_unlock_irqrestore(rdp, flags);
if (needwake_state)
swake_up_one(&rdp->nocb_state_wq);
