Messages in this thread | | | Date | Fri, 16 Mar 2012 11:06:52 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [tip:irq/core] genirq: Flush the irq thread on synchronization |
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On Fri, 16 Mar 2012, Ido Yariv wrote: > On Thu, Mar 15, 2012 at 08:07:56PM +0100, Alexander Gordeev wrote: > > Nevertheless, wake_threads_waitq() gets called and desc->threads_active gets > > decremented. As result, if desc->threads_active initially was decremented, we > > might wrongly wake up the queue while some threaded handler is still running. > > > > By contrast, if we choose not to wake up here, we might stuck in > > synchronize_irq(). Which is probably better than a fooling synchronize_irq(). > > AFAICT, IRQTF_RUNTHREAD and the desc->threads_active are always modified > together: > desc->threads_active is incremented if and only if IRQTF_RUNTHREAD is > set after being cleared (in irq_wake_thread()). > desc->threads_active is decremented in wake_threads_waitq(), which is > only called when IRQTF_RUNTHREAD is cleared. > > It seems that if we get to this point, either IRQTF_RUNTHREAD is set and > desc->threads_active was not decremented, or it is not set. > > Do you see any case where the two will be out of sync?
There is really no way, that the flag is set when we come out this regular exit path.
__free_irq() remove action synchronize_irq() kthread_stop()
So after the action is removed and synchronize_irq() made sure that the thread has finished IRQTF_RUNTHREAD cannot be set. Neither can we have a stale threads_oneshot bit set from this action.
That's a leftover of the old code and I really did not think it through fully and kept the stuff along with paranoid warnings.
I'm going to remove all of it.
Thanks,
tglx
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