On Tue, Jun 03, 2014 at 05:29:50PM -0700, Andy Lutomirski wrote: > Currently, the only real guarantee provided by the polling bit is > that, if you hold rq->lock and the polling bit is set, then you can > set need_resched to force a reschedule. > > The only reason the lock is needed is that the idle thread might not > be running at all when setting its need_resched bit, and rq->lock > keeps it pinned. > > This is easy to fix: just clear the polling bit before scheduling. > Now the polling bit is only ever set when rq->curr == rq->idle.
Yah, except of course:
lkml.kernel.org/r/20131120162736.508462...@infradead.org
which I really need to rebase and post again :/
In any case, this is useful even with that, although then we really must
do something like:
rcu_read_lock();
if (!set_nr_if_polling(rq->curr))
smp_send_reschedule(rq->cpu);
rcu_read_unlock();
Because there's other tasks than rq->idle which might be 'idle', joy!
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