Re: [Question] Quick Quiz B.13 help

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Mon, Feb 13, 2017 at 09:41:46PM +0800, Yubin Ruan wrote:
> Quick quiz B.13:
>     Suppose that lines 3-5 for CPUs 1 and 2 in Table B.4 are in an
> interrupt handler, and that the CPU 2's line 9 is running at process
> level. What changes, if any, are required to enable the code to work
> correctly, in other words, to prevent the assertion from firing?
> 
> I can not come up with any practical material for this quiz, because
> I don't really know the implication of "in an interrupt handler",
> and "running in process level".
> 
> The answer hints that one would need to ensure that the load of "e"
> precedes that of "a" and hint the Linux kernel implementation
> "barrier()". But how is that exactly? I am going to invest some time
> into the Linux kernel implementation. But I would really appreciate
> some hints about this, as I don't have so much kernel development
> experience before.

I suggest reading an operating-system textbook.  The ones I have are quite
old, but here they are anyway in bibtex format.  There are probably newer
editions of some of them.  The short answer on interrupts is that they
force process-level processing to pause while the "interrupt handler"
completes.

							Thanx, Paul

------------------------------------------------------------------------

@book{CorbetRubiniKroahHartman
,author="Jonathan Corbet and Alessandro Rubini and Greg Kroah-Hartman"
,title="Linux Device Drivers"
,publisher="O'Reilly Media, Inc."
,year="2005"
,edition="Third"
}

@book{Silberschatz98a
,author="Abraham Silberschatz and Peter Baer Galvin"
,title="Operating System Concepts"
,publisher="Addison-Wesley"
,year="1998"
,edition="Fifth"
}

@book{Vahalia96
,author="Uresh Vahalia"
,title="{UNIX} Internals: The New Frontiers"
,publisher="Prentice Hall"
,year="1996"
}