linux-kernel - Re: [RFC][PATCH 2/7] sched: Restructure destroy_sched

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Date:	Mon, 9 May 2016 16:46:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	mingo@...nel.org, linux-kernel@...r.kernel.org
Cc:	clm@...com, matt@...eblueprint.co.uk, mgalbraith@...e.de,
	tglx@...utronix.de, fweisbec@...il.com
Subject: Re: [RFC][PATCH 2/7] sched: Restructure destroy_sched_domain()

On Mon, May 09, 2016 at 12:48:09PM +0200, Peter Zijlstra wrote:
> There is no point in doing a call_rcu() for each domain, only do a
> callback for the root sched domain and clean up the entire set in one
> go.
> 
> Also make the entire call chain be called destroy_sched_domain*() to
> remove confusion with the free_sched_domains() call, which does an
> entirely different thing.
> 
> Both cpu_attach_domain() callers of destroy_sched_domain() can live
> without the call_rcu() because at those points the sched_domain hasn't
> been published yet.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---

This one seems to work much better; so much for last minute 'cleanups'.

---
 kernel/sched/core.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5824,10 +5824,8 @@ static void free_sched_groups(struct sch
 	} while (sg != first);
 }
 
-static void free_sched_domain(struct rcu_head *rcu)
+static void destroy_sched_domain(struct sched_domain *sd)
 {
-	struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
-
 	/*
 	 * If its an overlapping domain it has private groups, iterate and
 	 * nuke them all.
@@ -5841,15 +5839,21 @@ static void free_sched_domain(struct rcu
 	kfree(sd);
 }
 
-static void destroy_sched_domain(struct sched_domain *sd)
+static void destroy_sched_domains_rcu(struct rcu_head *rcu)
 {
-	call_rcu(&sd->rcu, free_sched_domain);
+	struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
+
+	while (sd) {
+		struct sched_domain *parent = sd->parent;
+		destroy_sched_domain(sd);
+		sd = parent;
+	}
 }
 
 static void destroy_sched_domains(struct sched_domain *sd)
 {
-	for (; sd; sd = sd->parent)
-		destroy_sched_domain(sd);
+	if (sd)
+		call_rcu(&sd->rcu, destroy_sched_domains_rcu);
 }
 
 /*