linux tasklets - order of execution

Question

At my university I am working on one project that involves some kernel programming. One part of this is loadable kernel module that registers interrupt handler for some given interrupt.

Now I have shared data structure that is used by interrupt handler and tasklets and I am wondering if I can be sure that tasklets are executed in the same order that they are scheduled or is it undefined?

For example my interrupt handler is called at time t1 and time t2, each invocation executes tasklet_schedule(&customTasklet);. Now, can I be sure that the tasklet that was scheduled at time t1 will be executed first?

Federico · Accepted Answer · 2013-11-19T10:23:05.090

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Scheduled tasklet are stored within a list; the system read this list in FIFO order, so: yes t1 is executed before t2.

Here some code to understand the mechanism.

edit

As reminded by CL, there is a tasklet list for each CPU; so when you shedule a tasklet, you are scheduling it on the active CPU. So tasklet are serialized on the same CPU. If you schedule t1 un CPU1 and t2 on CPU2 it may happen that t2 is executed before t1.

edited Nov 19 '13 at 10:23

answered Nov 18 '13 at 14:57

Federico

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… if the tasklets were scheduled on the same CPU. – CL. Nov 18 '13 at 15:35
Ok, thanks for the answer, but what if the CPU has more then one thread? Is it for each physical CPU? – Andna Nov 19 '13 at 10:52
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I am not 100% sure about this. But I think is for each physical CPU (core). – Federico Nov 19 '13 at 23:13

linux tasklets - order of execution

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