netdev - [PATCH] rhashtable: use irq-safe spinlock in rhashtable_rehash

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Message-Id: <20190205143706.28371-1-johannes@sipsolutions.net>
Date:   Tue,  5 Feb 2019 15:37:06 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     Jouni Malinen <j@...fi>, Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH] rhashtable: use irq-safe spinlock in rhashtable_rehash_table()

From: Johannes Berg <johannes.berg@...el.com>

When an rhashtabl walk is done from irq/bh context, we rightfully
get a lockdep complaint saying that we could get a (soft-)IRQ in
the middle of a rehash. This happened e.g. in mac80211 as it does
a walk in soft-irq context.

Fix this by using irq-safe locking here. We don't need _irqsave()
as we know this will be called only in process context from the
workqueue. We could get away with _bh() but that seems a bit less
generic, though I'm not sure anyone would want to do a walk from
a real IRQ handler.

Reported-by: Jouni Malinen <j@...fi>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 lib/rhashtable.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 852ffa5160f1..ad3c1da15475 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -327,10 +327,10 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
 	/* Publish the new table pointer. */
 	rcu_assign_pointer(ht->tbl, new_tbl);
 
-	spin_lock(&ht->lock);
+	spin_lock_irq(&ht->lock);
 	list_for_each_entry(walker, &old_tbl->walkers, list)
 		walker->tbl = NULL;
-	spin_unlock(&ht->lock);
+	spin_unlock_irq(&ht->lock);
 
 	/* Wait for readers. All new readers will see the new
 	 * table, and thus no references to the old table will
-- 
2.17.2