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 cpu and rtnl locking starvation problem.
This patch releases the cpu and rtnl lock when link watch worker has processed a fixed number of netdev' link watch event. Currently __linkwatch_run_queue is called with rtnl lock, so enfore it with ASSERT_RTNL(); Signed-off-by: Yunsheng Lin <[email protected]> --- V2: use cond_resched and rtnl_unlock after processing a fixed number of events --- net/core/link_watch.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/net/core/link_watch.c b/net/core/link_watch.c index 7f51efb..07eebfb 100644 --- a/net/core/link_watch.c +++ b/net/core/link_watch.c @@ -168,9 +168,18 @@ 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); + ASSERT_RTNL(); + + /* 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 @@ -200,6 +209,14 @@ static void __linkwatch_run_queue(int urgent_only) } spin_unlock_irq(&lweventlist_lock); linkwatch_do_dev(dev); + + if (--do_dev < 0) { + rtnl_unlock(); + cond_resched(); + do_dev = MAX_DO_DEV_PER_LOOP; + rtnl_lock(); + } + spin_lock_irq(&lweventlist_lock); } -- 2.8.1
