linux-kernel - Re: [PATCH 07/16] rcu/nocb: Rename nocb_gp_update_state to nocb_gp_update_state

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Date:   Thu, 28 Jan 2021 16:49:44 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Josh Triplett <josh@...htriplett.org>,
        Stable <stable@...r.kernel.org>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 07/16] rcu/nocb: Rename nocb_gp_update_state to
 nocb_gp_update_state_deoffloading

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@...nel.org>
> Cc: Josh Triplett <josh@...htriplett.org>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Cc: Joel Fernandes <joel@...lfernandes.org>
> Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

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@...nel.org>
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@...nel.org>
    Cc: Josh Triplett <josh@...htriplett.org>
    Cc: Lai Jiangshan <jiangshanlai@...il.com>
    Cc: Joel Fernandes <joel@...lfernandes.org>
    Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
    Cc: Boqun Feng <boqun.feng@...il.com>
    Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

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);