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All is in the title. Any links to good documentations are welcome.
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An interrupt is simply a signal that the hardware can send when it wants the processor's attention. Linux handles interrupts in much the same way that it handles signals in user space. For the most part, a driver need only register a handler for its device's interrupts, and handle them properly when they arrive.
Definition of local time : time based on the meridian through a particular place as contrasted with that of a time zone.
remember: timers are independent of the CPU. time period t (also called as clock period). interrupt is generated in every cycle. by the user.
The Timer/Counter Interrupt Flag Register. The OCF2 bit is set (one) when a compare match occurs between the Timer/Counter2 and the data in OCR2 - Output Compare Register 2. OCF2 is cleared by hardware when executing the corresponding interrupt handling vector.
On SMP systems apic timer is used for scheduler / rescheduling threads.
On UP system pit timer is used for scheduler / rescheduling threads.
Normaly the PIT is no longer used anymore in SMP systems.
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A less technical answer than Michael Burr's:
Some things need to be done every jiffy, doesn't matter on which CPU.
Other things need to be done every jiffy on each CPU. For example, checking if we need to switch to another process.
The local timer interrupt exists for the second type - whenever it's executed, we check them and do what's needed.
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