Hello! On 10/11/2019 08:15 PM, Sebastian Andrzej Siewior wrote:
> From: Marc Kleine-Budde <m...@pengutronix.de> > > With threaded interrupts enabled, the interrupt thread runs as SCHED_RR > with priority 50. If a user application with a higher priority preempts > the interrupt thread and tries to shutdown the network interface then it > will loop forever. The kernel will spin in the loop waiting for the > device to become idle and the scheduler will never consider the > interrupt thread because its priority is lower. > > Avoid the problem by using by sleeping for a jiffy giving other tasks, So "using" or "sleeping"? :-) > including the interrupt thread, a chance to run and make progress. > > In the original thread it has been suggested to use wait_event() and > properly waiting for the state to occur. DaveM explained that this would > require to add expensive checks in the fast paths of packet processing. > > Link: > https://lkml.kernel.org/r/1393976987-23555-1-git-send-email-...@pengutronix.de > Signed-off-by: Marc Kleine-Budde <m...@pengutronix.de> > [bigeasy: Rewrite commit message, add comment, use > schedule_timeout_uninterruptible()] > Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> > --- > > The old thread also pointed anoth yield() loop which was resolved by > commit > 845704a535e9b ("tcp: avoid looping in tcp_send_fin()") > > net/sched/sch_generic.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c > index 17bd8f539bc7f..b27574f2c6b47 100644 > --- a/net/sched/sch_generic.c > +++ b/net/sched/sch_generic.c > @@ -1217,8 +1217,13 @@ void dev_deactivate_many(struct list_head *head) > > /* Wait for outstanding qdisc_run calls. */ > list_for_each_entry(dev, head, close_list) { > - while (some_qdisc_is_busy(dev)) > - yield(); > + while (some_qdisc_is_busy(dev)) { > + /* wait_event() would avoid this sleep-loop but would > + * require expesive checks in the fast paths of packet Expensive? > + * processing which isn't worth it. > + */ > + schedule_timeout_uninterruptible(1); > + } > /* The new qdisc is assigned at this point so we can safely > * unwind stale skb lists and qdisc statistics > */ MBR, Sergei
