Hey Sreejith, softirq's are run as bottom half processing (after an interrupt is handled or when there is no work to be done - https://www.kernel.org/doc/htmldocs/kernel-hacking/basics-softirqs.html ) and sched_softirq is one such soft irq whose only function is confined to the routine run_rebalance_domain(). __schedule() is the main scheduling function that tries to pick the next task and then perform context switch and other associated scheduling functions. Since run_rebalance_domain() need not be run at that exact time frame, it is scheduled for later time when the cpu can take it up using softirq's. Therefore __schedule() need not be called in this softirq context as such because these are independent operations. Hope this helps. Thanks and regards, Vignesh Radhakrishnan On Wed, Jan 28, 2015 at 10:25 PM, Sreejith M M <sreejith.mm@gmail.com> wrote:
Hi,
I was reading LKD by Robert Love. I got the following idea from the book.
Correct me if I am worng I was checking through source code and I found that on every timer interrupt, through sched/fair.c we are raising the SCHED_SOFTIRQ(). I was checking the relation between SCHED_SOFTIRQ and actual __schedule() function.
My assumption: schedule() function is the function which selects the processes which are ready to run in run queue. schedule() function is called in every timer tick.
What I was thinking is that schedule() will be called as part of handling SCHED_SOFTIRQ() . But in source code, SCHED_SOFTIRQ is handled through run_rebalance_domain() function (sched/fair.c) . I am unable to trace __schedule() from this function.
Am I missing anything or my assumptions are wrong? -- Regards, Sreejith
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