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 <[email protected]> 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 > > _______________________________________________ > Kernelnewbies mailing list > [email protected] > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > -- http://vigneshradhakrishnan.blogspot.com/
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