Messages in this thread | | | Date | Mon, 18 Jun 2012 10:08:27 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC patch 5/5] infiniband: ehca: Use hotplug thread infrastructure |
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On Mon, 18 Jun 2012, Rusty Russell wrote:
> On Wed, 13 Jun 2012 11:00:56 -0000, Thomas Gleixner <tglx@linutronix.de> wrote: > > @@ -662,10 +663,15 @@ static inline int find_next_online_cpu(s > > ehca_dmp(cpu_online_mask, cpumask_size(), ""); > > > > spin_lock_irqsave(&pool->last_cpu_lock, flags); > > - cpu = cpumask_next(pool->last_cpu, cpu_online_mask); > > - if (cpu >= nr_cpu_ids) > > - cpu = cpumask_first(cpu_online_mask); > > - pool->last_cpu = cpu; > > + while (1) { > > + cpu = cpumask_next(pool->last_cpu, cpu_online_mask); > > + if (cpu >= nr_cpu_ids) > > + cpu = cpumask_first(cpu_online_mask); > > + pool->last_cpu = cpu; > > + /* Might be on the way out */ > > + if (per_cpu_ptr(pool->cpu_comp_tasks, cpu)->active) > > + break; > > + } > > Heh, isn't this what we used to call a "do while" loop? :)
Yep :)
> Your infrastructure is a really weird mix. On the one hand, it's a set > of callbacks: setup, cleanup, park, unpark. Cool. > > On the other hand, instead of a 'run' callback, you've got a thread_fn, > which has to loop and call smpboot_thread_check_parking(). > > If you just had the thread_fn, it'd be trivial to follow program flow. > If you just had the callbacks, it'd still be pretty easy, though it > seems like a little too much help.
The reason why I moved stuff into the callbacks and have the state machine inside of smpboot_check_kthread_parking() is that every user has to do that. i.e. keep track of the state so you wont setup/teardown stuff twice.
Now look at that function and copy it into all users of the park infrastructure. Not pretty. I had it that way and it was fugly as hell. That's why I came up with the callbacks and the generic state machine.
> As it is, we have Paul doing setup stuff inside his thread_fn: > > + trace_rcu_utilization("Start CPU kthread@unpark"); > + sp.sched_priority = RCU_KTHREAD_PRIO; > + sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
I fixed that already :)
Thanks,
tglx
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