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I am currently reading xv6 kernel source ported to 32bit x86. My question is regarding blocking io syscall, i.e., bread. I am expecting some trap handler in xv6 that sets its own process state to SLEEPING and calls yield(). However, I don't see any code fragment in xv6 kernel source. Please advise me if I missed the code fragment in the existing xv6 kernel source, or whether this is what students suppose to implement as a course project or not.

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  • Can you give a link to the exact version of the source you are working with? Commented Aug 27 at 20:00
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    Reading from disk is typically not blocking in the usual sense. So maybe you should look for another example. For the RISC-V version, you can see here what wait() does when no children have exited: it calls sleep(), which does just what you suggested: p->state = SLEEPING; sched();. Commented Aug 27 at 20:03
  • I download the xv6-pub 2006 32bit x86. I just tried "git clone git://github.com/mit-pdos/xv6-public.git", but the link seems no longer accessible. As you pointed out, I see the wait() system call does in x86 version of xv6. However, not the I/O. I will inspect RISC-V version as you suggested. Thank you! Commented Sep 1 at 16:14
  • I understand how wait() works. I still don't see any mechanism to make a process that initiates I/0 from RUNNING to SLEEPING in xv6 (github.com/mit-pdos/xv6-public). Commented Sep 2 at 13:52
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