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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 <jasowang@redhat.com>
============================================
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" <amritha.nambiar@intel.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Fixes: 8af2c06ff4
("net-sysfs: Add interface for Rx queue(s) map per Tx queue")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
4005a7cb4f
commit
4d99f6602c
@ -1903,9 +1903,11 @@ static void virtnet_set_affinity(struct virtnet_info *vi)
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i = 0;
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for_each_online_cpu(cpu) {
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const unsigned long *mask = cpumask_bits(cpumask_of(cpu));
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virtqueue_set_affinity(vi->rq[i].vq, cpu);
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virtqueue_set_affinity(vi->sq[i].vq, cpu);
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netif_set_xps_queue(vi->dev, cpumask_of(cpu), i);
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__netif_set_xps_queue(vi->dev, mask, i, false);
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i++;
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}
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@ -2176,6 +2176,7 @@ static void netif_reset_xps_queues(struct net_device *dev, u16 offset,
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if (!static_key_false(&xps_needed))
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return;
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cpus_read_lock();
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mutex_lock(&xps_map_mutex);
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if (static_key_false(&xps_rxqs_needed)) {
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@ -2199,10 +2200,11 @@ static void netif_reset_xps_queues(struct net_device *dev, u16 offset,
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out_no_maps:
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if (static_key_enabled(&xps_rxqs_needed))
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static_key_slow_dec(&xps_rxqs_needed);
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static_key_slow_dec_cpuslocked(&xps_rxqs_needed);
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static_key_slow_dec(&xps_needed);
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static_key_slow_dec_cpuslocked(&xps_needed);
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mutex_unlock(&xps_map_mutex);
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cpus_read_unlock();
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}
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static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
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@ -2250,6 +2252,7 @@ static struct xps_map *expand_xps_map(struct xps_map *map, int attr_index,
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return new_map;
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}
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/* Must be called under cpus_read_lock */
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int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
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u16 index, bool is_rxqs_map)
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{
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@ -2317,9 +2320,9 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
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if (!new_dev_maps)
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goto out_no_new_maps;
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static_key_slow_inc(&xps_needed);
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static_key_slow_inc_cpuslocked(&xps_needed);
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if (is_rxqs_map)
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static_key_slow_inc(&xps_rxqs_needed);
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static_key_slow_inc_cpuslocked(&xps_rxqs_needed);
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for (j = -1; j = netif_attrmask_next(j, possible_mask, nr_ids),
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j < nr_ids;) {
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@ -2448,11 +2451,18 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
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kfree(new_dev_maps);
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return -ENOMEM;
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}
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EXPORT_SYMBOL_GPL(__netif_set_xps_queue);
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int netif_set_xps_queue(struct net_device *dev, const struct cpumask *mask,
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u16 index)
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{
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return __netif_set_xps_queue(dev, cpumask_bits(mask), index, false);
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int ret;
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cpus_read_lock();
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ret = __netif_set_xps_queue(dev, cpumask_bits(mask), index, false);
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cpus_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL(netif_set_xps_queue);
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@ -26,6 +26,7 @@
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#include <linux/pm_runtime.h>
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#include <linux/of.h>
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#include <linux/of_net.h>
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#include <linux/cpu.h>
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#include "net-sysfs.h"
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@ -1400,7 +1401,10 @@ static ssize_t xps_rxqs_store(struct netdev_queue *queue, const char *buf,
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return err;
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}
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cpus_read_lock();
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err = __netif_set_xps_queue(dev, mask, index, true);
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cpus_read_unlock();
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kfree(mask);
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return err ? : len;
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}
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