Re: [Xen-devel] generate random numbers

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

If you want us to spend some of our time helping you, you need to 
demonstrate that you've tried to spend some time helping yourself.  How 
might rc come to be 0 at that line?  What is remove_entry() doing?  How 
could this have come about because of something your code did?
An example mail that would get more help would be something like this:

"I've looked at the remove_entry() function, and it seems that the bug 
can be triggered if the input is {some condition}.  I looked at where 
remove_entry() is being called, but I can't figure out how it can get 
that condition because of my code."
-George

michele.paolino wrote:
> Line 184 correspond at rc = 0 (an int variable) of remove_entry() 
> function. I don't have modified that file.
> Michele
>
>
> On Fri, Feb 26, 2010 at 6:44 PM, George Dunlap 
> <george.dunlap@xxxxxxxxxxxxx <mailto:george.dunlap@xxxxxxxxxxxxx>> wrote:
>     Did you look at timer.c, line 184, to find out what the BUG is?
>     -George
>
>     michele.paolino wrote:
>
>         Following George's advices I have rewrited my scheduler. But
>         now serial console's log report me a bug in a function of timer.c
>
>         (XEN) ****************************************
>         (XEN) Panic on CPU 0:
>         (XEN) Xen BUG at timer.c:184
>         (XEN) ****************************************
>
>         This is caused by cpumask_raise_softirq() in my wake()
>         function. What can I do?
>
>         Michele
>
>         On Thu, Feb 25, 2010 at 10:25 PM, George Dunlap
>         <george.dunlap@xxxxxxxxxxxxx
>         <mailto:george.dunlap@xxxxxxxxxxxxx>
>         <mailto:george.dunlap@xxxxxxxxxxxxx
>         <mailto:george.dunlap@xxxxxxxxxxxxx>>> wrote:
>
>            The problem is that you're choosing a random vcpu to run,
>         without
>            considering whether it *wants* to run or not.  In this case,
>            you're running a vcpu before it's even been completely set
>         up yet
>            (write_cr3 is failing because the guest *has* no cr3 ready
>         yet).
>
>            The normal way schedulers deal with this is to keep one list of
>            all vcpus (or all domains), and another list with "runnable"
>            vcpus.  You can keep track of which vcpus are runnable with the
>            vcpu_wake() callback and by using vcpu_runnable() in
>         schedule().
>
>            At very least, your loop in schedule should check
>         vcpu_runnable()
>            before selecting it.
>
>            -George
>
>
>            michele.paolino wrote:
>
>                Here's my random scheduler. It works until I start a
>         virtual
>                machine (error file attached is the serial console's log).
>                In xen call trace there isn't any of my functions.
>                To generate random numbers I'm using the hash (MD5) of
>         NOW()
>                function.
>                I would also Know why at boot time there are two calls at
>                vcpu_init function for vcpu with id = 0 ??
>
>                Thanks
>                Michele

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