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Old 11-29-2005, 08:48 PM   #1
lucky6969b
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Linux Interrupt Handler


Hi,
Are Linux Interrupt handler basically the same as DOS? Also, how to write an interrupt handler for NMI? Just very generally
Thanks
Jack
 
Old 12-01-2005, 11:55 AM   #2
sundialsvcs
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Interrupts are handled by the kernel, usually in device-drivers. The best place to learn about them is to look at some of the driver source-code in your kernel.

The Linux Documentation Project (TLDP) has several articles on the subject, including this relevant chapter of the Module Programming guide.

If you like to read books in the loo , not just online (that is, I hope you don't have a computer there!), then there are many good titles on O'Reilly Publishing's web-site, such as this one.

It is very important to understand the complete relationship of the various parts of the kernel. In DOS, there is no multitasking, no virtual memory. In Linux, you might be sharing the world with eight other CPUs and a thousand active processes. So, the interrupt handling system is logically split into two parts, sometimes called the "top half" and the "bottom half." (There was, at one time, a mechanism called TH/BH, now generally superseded by tasklets.) Anyhow, the essential idea is that the hardware interrupt itself (the "top half") is essentially only a signal that causes the "real" work, in the "bottom half," to be immediately scheduled. But you also have issues to consider, like what happens if the process that requested the I/O operation has been swapped-out while waiting? What if the user, accidentally or deliberately, specified a memory-address that he does not own, or owns but is not permitted to write to? And the address, of course, is virtual, not real.

It's not extraordinarily difficult but it is tricky. You can often base your work on an existing production driver, copying it and changing only the essential parts of the code.
 
  


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