netdev - [PATCH 1/4] net: move setup code out of mutex in __netif_set_xps

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Date:   Sun,  2 Oct 2022 08:16:59 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Menglong Dong <imagedong@...cent.com>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Petr Machata <petrm@...dia.com>, linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH 1/4] net: move setup code out of mutex in __netif_set_xps_queue()

maps_sz, nr_ids and online_mask may be set out of the mutex.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 net/core/dev.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 56c8b0921c9f..b848a75026c4 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2563,9 +2563,6 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 			return -EINVAL;
 	}
 
-	mutex_lock(&xps_map_mutex);
-
-	dev_maps = xmap_dereference(dev->xps_maps[type]);
 	if (type == XPS_RXQS) {
 		maps_sz = XPS_RXQ_DEV_MAPS_SIZE(num_tc, dev->num_rx_queues);
 		nr_ids = dev->num_rx_queues;
@@ -2579,6 +2576,10 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
 	if (maps_sz < L1_CACHE_BYTES)
 		maps_sz = L1_CACHE_BYTES;
 
+	mutex_lock(&xps_map_mutex);
+
+	dev_maps = xmap_dereference(dev->xps_maps[type]);
+
 	/* The old dev_maps could be larger or smaller than the one we're
 	 * setting up now, as dev->num_tc or nr_ids could have been updated in
 	 * between. We could try to be smart, but let's be safe instead and only
-- 
2.34.1