On 03/06/2014 10:06 PM, David Miller wrote: > From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> > Date: Wed, 5 Mar 2014 00:49:47 +0100 > >> @@ -839,7 +839,7 @@ void dev_deactivate_many(struct list_head *head) >> /* Wait for outstanding qdisc_run calls. */ >> list_for_each_entry(dev, head, unreg_list) >> while (some_qdisc_is_busy(dev)) >> - yield(); >> + msleep(1) >> } > > I don't understand this. > > yield() should really _mean_ yield. > > The intent of a yield() call, like this one here, is unambiguously > that the current thread cannot do anything until some other thread > gets onto the cpu and makes forward progress. > > Therefore it should allow lower priority threads to run, not just > equal or higher priority ones. Yes, we need a call that does what you described, however I'm not sure if yield() really does that. According to: http://lxr.free-electrons.com/source/kernel/sched/core.c#L3599 > * Typical broken usage is: > * > * while (!event) > * yield(); > * > * where one assumes that yield() will let 'the other' process run that will > * make event true. If the current task is a SCHED_FIFO task that will never > * happen. Never use yield() as a progress guarantee!! My Process runs with SCHED_FIFO and prio > 50, with IRQ at default prio, which is 50. Maybe the RT guys can comment on this. I found another interesting function in the RT patch set: cpu_chill(). Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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