From 4d99f6602cb552fb58db0c3b1d935bb6fa017f24 Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Wed, 8 Aug 2018 20:07:35 -0700 Subject: net: allow to call netif_reset_xps_queues() under cpus_read_lock The definition of static_key_slow_inc() has cpus_read_lock in place. In the virtio_net driver, XPS queues are initialized after setting the queue:cpu affinity in virtnet_set_affinity() which is already protected within cpus_read_lock. Lockdep prints a warning when we are trying to acquire cpus_read_lock when it is already held. This patch adds an ability to call __netif_set_xps_queue under cpus_read_lock(). Acked-by: Jason Wang ============================================ WARNING: possible recursive locking detected 4.18.0-rc3-next-20180703+ #1 Not tainted -------------------------------------------- swapper/0/1 is trying to acquire lock: 00000000cf973d46 (cpu_hotplug_lock.rw_sem){++++}, at: static_key_slow_inc+0xe/0x20 but task is already holding lock: 00000000cf973d46 (cpu_hotplug_lock.rw_sem){++++}, at: init_vqs+0x513/0x5a0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(cpu_hotplug_lock.rw_sem); lock(cpu_hotplug_lock.rw_sem); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by swapper/0/1: #0: 00000000244bc7da (&dev->mutex){....}, at: __driver_attach+0x5a/0x110 #1: 00000000cf973d46 (cpu_hotplug_lock.rw_sem){++++}, at: init_vqs+0x513/0x5a0 #2: 000000005cd8463f (xps_map_mutex){+.+.}, at: __netif_set_xps_queue+0x8d/0xc60 v2: move cpus_read_lock() out of __netif_set_xps_queue() Cc: "Nambiar, Amritha" Cc: "Michael S. Tsirkin" Cc: Jason Wang Fixes: 8af2c06ff4b1 ("net-sysfs: Add interface for Rx queue(s) map per Tx queue") Signed-off-by: Andrei Vagin Signed-off-by: David S. Miller --- drivers/net/virtio_net.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/net/virtio_net.c') diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 62311dde6e71..39a7f4452587 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1903,9 +1903,11 @@ static void virtnet_set_affinity(struct virtnet_info *vi) i = 0; for_each_online_cpu(cpu) { + const unsigned long *mask = cpumask_bits(cpumask_of(cpu)); + virtqueue_set_affinity(vi->rq[i].vq, cpu); virtqueue_set_affinity(vi->sq[i].vq, cpu); - netif_set_xps_queue(vi->dev, cpumask_of(cpu), i); + __netif_set_xps_queue(vi->dev, mask, i, false); i++; } -- cgit