Spurious Interrupt

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Message-ID: <37A18B65.3AD8F1AA@aplawrence.com>
Date: Fri, 30 Jul 1999 07:24:21 -0400
Subject: Re: Problem with NOTICE Sdsk and Spurious Interrupts revisited
References: <rq2td1$0$37nspbi$3e@corp.supernews.com>

A spurious interrupt is an interrupt the driver didn't expect.

Briefly, devices such as disks, parallel ports, serial ports, etc. use interrupts to signal back to the cpu that they have completed the last task you gave them. The rationale behind this is that devices are very slow; you can hand them data, and there is room for thousands or even millions of other cpu instructions to be done before that device is ready to handle more data. Interrupts can also signal a need for attention: a serial port recieving characters sends interrupts letting the driver know that new data has arrived.

So a spurious interrupt is unexpected. You didn't give the damn thing any data, so why is it tapping you on the shoulder looking for attention? You could also have the case of an interrupt on a line that isn't configured at all: say the kernel hasn't been told of any device using interrupt 11, but whoops, there it is. That generates a different message, though.

See /Unixart/devices.html and /Unixart/driverart.html for more information.

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