Re: [PATCH 01/10] scsi/mvsas: Kill CONFIG_SCSI_MVSAS_TASKLET

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2022-05-31 16:26:26 [+0100], John Garry wrote:
> On 31/05/2022 16:17, Sebastian Andrzej Siewior wrote:
> > > Sorry, maybe I was not clear, but I was just asking if there was a good
> > > reason to disable interrupts at source while handling the interrupt, and not
> > > the change to stop using a tasklet.
> > Without reading the patch first: You need to disable the interrupt
> > source while the tasklet/ threaded interrupt is handled. Otherwise the
> > interrupt will keep coming and the tasklet/ threaded interrupt will have
> > no chance to make progress. So the box will lock up. This is often
> > overseen on fast machines because the interrupt needs a few usecs to
> > trigger and so the CPU is able to make a little bit of progress between
> > each trigger.
> > 
> 
> ah, so we would need IRQF_ONESHOT flag set to keep the interrupt line
> disabled until the threaded part completes, right?

This is one way of doing it and this is what threaded irqs do. However
this requires all handler to specify that option which is not very
compatible with shared handler.

> Thanks,
> John

Sebastian