linux-kernel - Re: [PATCH] serial: 8250 check iir rdi in interrupt

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Message-ID: <20121023110133.62bed522@pyramind.ukuu.org.uk>
Date:	Tue, 23 Oct 2012 11:01:33 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Min Zhang <mzhang@...sta.com>
Cc:	gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: 8250 check iir rdi in interrupt

> Added module parameter skip_rdi_check to opt out this workaround.

NAK. Anything like this should be runtime.

> Tested on Radisys ATCA 46XX which uses FPGA 16550-compatible and
> other generic 16550 UART. It takes from an hour to days to reproduce by
> pumping inputs to serial console continously using TeraTerm script:

You turn this on by default but it's a nasty IRQ latency penalty
on a lot of x86 platforms with the uarts on the lpc bus.

What I am not clear on from this is

- do you see it on both the ports (the bug that is)
- if you do see it on both are you sure its not in reality a symptom of
  some other console/irq handling race ?

Alan
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