Re: [PATCH v2 04/19] PCI: serialize hotplug operations triggered byPCI hotplug sysfs interfaces

[Jiang Liu]

On 2012-5-2 13:06, Greg KH wrote:
> On Fri, Apr 27, 2012 at 11:16:45PM +0800, Jiang Liu wrote:
> > +	/* Avoid deadlock with pci_hp_deregister() */
> > +	while (!pci_hotplug_try_enter()) {
> > +		/* Check whether the slot has been deregistered. */
> > +		if (list_empty(&slot->slot_list)) {
> > +			retval = -ENODEV;
> > +			goto exit_put;
> > +		}
> > +		msleep(1);
> > +	}
>
> Oh my.
>
> Wow.
>
> {sigh}
>
> ick.
>
> My eyes hurt.
>
> And your cpu load just went crazy.
>
> You can now handle all of the nasty emails from sysadmins asking why
> their systems look like their load is high for no good reason.
My bad, should use schedule_timeout_interruptible() instead of
msleep(1) here to avoid busy waiting.

> Not to mention all of the other issues here.
>
> My statement about not inventing new lock types has now been proven
> true.
>
> The fact that this would even be a chunk of code that was proposed to be
> merged makes me weep.
>
> You owe me a bottle of whatever you are drinking if you expect me to
> continue to review these patch submissions.
>
> I'm stopping here in the series, please rework this whole thing in a
> major way.
>
> greg k-h


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