Re: Whats bottom halfs for then?

[Usman Ansari <uansari@xxxxxxxxx>]

Interrupts are ran immediately & asynchronously and the and perform time 
sensitive work, like acknoldge to hardware, copy buffer, etc usually 
stuff related to hardware. While bottom half are ran with interrupts 
enabled and they are ran when it is convenient for the system.

You acquire spinlocks in interrupt context.

Now there are variety of way for implementing bottom halfs, for 2.6 old 
BH and Task queues has been removed and is replaced by Softirq, Tasklet 
and Work queues.

Softirqs are really for important and time critical work like servicing 
RX & TX network traffic, timer interrupt and Tasklet. For your driver 
most obvious choice is Tasklets. Softirqs and Tasklet are present in 2.4 
also. Work queues are new in 2.6.Work queue also provide process context.

Suggest "Linux Kernel Development" by Robert Love.

Usman

--
Usman S. Ansari
http://beconvinced.com



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