From 195648bbc5ae0848e82f771ecf4cd7497054c212 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 19 Aug 2008 04:00:36 -0700 Subject: [PATCH] pkt_sched: Prevent livelock in TX queue running. If dev_deactivate() is trying to quiesce the queue, it is theoretically possible for another cpu to livelock trying to process that queue. This happens because dev_deactivate() grabs the queue spinlock as it checks the queue state, whereas net_tx_action() does a trylock and reschedules the qdisc if it hits the lock. This breaks the livelock by adding a check on __QDISC_STATE_DEACTIVATED to net_tx_action() when the trylock fails. Based upon feedback from Herbert Xu and Jarek Poplawski. Signed-off-by: David S. Miller --- net/core/dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/core/dev.c b/net/core/dev.c index 8d133802372..60c51f76588 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1990,7 +1990,9 @@ static void net_tx_action(struct softirq_action *h) qdisc_run(q); spin_unlock(root_lock); } else { - __netif_reschedule(q); + if (!test_bit(__QDISC_STATE_DEACTIVATED, + &q->state)) + __netif_reschedule(q); } } } -- 2.41.1