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net: link_watch: prevent starvation when processing linkwatch wq 

When user has configured a large number of virtual netdev, such
as 4K vlans, the carrier on/off operation of the real netdev
will also cause it's virtual netdev's link state to be processed
in linkwatch. Currently, the processing is done in a work queue,
which may cause rtnl locking starvation problem and worker
starvation problem for other work queue, such as irqfd_inject wq.

This patch releases the cpu when link watch worker has processed
a fixed number of netdev' link watch event, and schedule the
work queue again when there is still link watch event remaining.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yunsheng Lin 2019-06-28 09:13:19 +08:00 committed by David S. Miller
parent 0d0bcacc54
commit 27ba4059e0
1 changed files with 12 additions and 1 deletions
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13
net/core/link_watch.c
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@ -163,9 +163,16 @@ static void linkwatch_do_dev(struct net_device *dev)
static void __linkwatch_run_queue(int urgent_only)
{
#define MAX_DO_DEV_PER_LOOP 100
int do_dev = MAX_DO_DEV_PER_LOOP;
struct net_device *dev;
LIST_HEAD(wrk);
/* Give urgent case more budget */
if (urgent_only)
do_dev += MAX_DO_DEV_PER_LOOP;
/*
* Limit the number of linkwatch events to one
* per second so that a runaway driver does not
@ -184,7 +191,7 @@ static void __linkwatch_run_queue(int urgent_only)
spin_lock_irq(&lweventlist_lock);
list_splice_init(&lweventlist, &wrk);
while (!list_empty(&wrk)) {
while (!list_empty(&wrk) && do_dev > 0) {
dev = list_first_entry(&wrk, struct net_device, link_watch_list);
list_del_init(&dev->link_watch_list);
@ -195,9 +202,13 @@ static void __linkwatch_run_queue(int urgent_only)
}
spin_unlock_irq(&lweventlist_lock);
linkwatch_do_dev(dev);
do_dev--;
spin_lock_irq(&lweventlist_lock);
}
/* Add the remaining work back to lweventlist */
list_splice_init(&wrk, &lweventlist);
if (!list_empty(&lweventlist))
linkwatch_schedule_work(0);
spin_unlock_irq(&lweventlist_lock);