Re: [PATCH 2/3] serial: stm32: fix threaded interrupt handling

[Johan Hovold]

On Fri, Apr 16, 2021 at 10:35:25PM +0800, dillon min wrote:
> Hi Johan
> 
> Thanks for share your patch.
> 
> Johan Hovold <johan@xxxxxxxxxx>于2021年4月16日 周五22:11写道：
> 
> > When DMA is enabled the receive handler runs in a threaded handler, but
> > the primary handler up until very recently neither disabled interrupts
> > in the device or used IRQF_ONESHOT. This would lead to a deadlock if an
> > interrupt comes in while the threaded receive handler is running under
> > the port lock.
> >
> Greg told me there was a patch fixed this case. In case hard irq &
> threaded_fn both offered. The local_irq_save() will be executed before call
> driver’s threaded handler.
> 
> Post the original mail from Greg
> 
> Please see 81e2073c175b ("genirq: Disable interrupts for force threaded
> handlers") for when threaded irq handlers have irqs disabled, isn't that
> the case you are trying to "protect" from here?
> 
> Why is the "threaded" flag used at all?  The driver should not care.
> 
> Also see 9baedb7baeda ("serial: imx: drop workaround for forced irq
> threading") in linux-next for an example of how this was fixed up in a
> serial driver.

Neither of these commits are (directly) related to the problem this
patch addresses (they are about force-threaded handlers, this is about a
normal threaded handler which run with interrupts enabled).

Johan