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Patrick McHardy
0621ed2e4e
As noticed by Ranko Zivojnovic <[email protected]>, calling qdisc_run from the timer handler can result in deadlock: > CPU#0 > > qdisc_watchdog() fires and gets dev->queue_lock > qdisc_run()...qdisc_restart()... > -> releases dev->queue_lock and enters dev_hard_start_xmit() > > CPU#1 > > tc del qdisc dev ... > qdisc_graft()...dev_graft_qdisc()...dev_deactivate()... > -> grabs dev->queue_lock ... > > qdisc_reset()...{cbq,hfsc,htb,netem,tbf}_reset()...qdisc_watchdog_cancel()... > -> hrtimer_cancel() - waiting for the qdisc_watchdog() to exit, while still > holding dev->queue_lock > > CPU#0 > > dev_hard_start_xmit() returns ... > -> wants to get dev->queue_lock(!) > > DEADLOCK! The entire optimization is a bit questionable IMO, it moves potentially large parts of NET_TX_SOFTIRQ work to TIMER_SOFTIRQ/HRTIMER_SOFTIRQ, which kind of defeats the separation of them. Signed-off-by: Patrick McHardy <[email protected]> Acked-by: Ranko Zivojnovic <[email protected]> Signed-off-by: David S. Miller <[email protected]>