On Fri, Apr 16, 2021 at 10:35:25PM +0800, dillon min wrote:

Hi Johan

Thanks for share your patch.

Johan Hovold johan@kernel.org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