On 4/23/06, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
> Hi...
>
> > I found that the kernel is preemptible and context switch happened.
> Hm..ok...
>
> > but printk() always print wrong msg,
> > ex
> > this is thread 1, loop 1
> > this is thread 1, loop 2
> > this is thread 2, loop 2000
> "loop"? you print "loop"? I didn't see it in your code..CMIIW
>
Hi Min-Hua,
Can you please pasteyour experimental code once again and the results
you are finding.
> > I don't know if printk has a buffer and will overflow in this situation.
> > I used spinlock for this:
> >
> > spin_lock();
> > printk("this is process %d\n",current->pid);
> > spin_unlock();
> >
See with CONFIG_PREEMPT on, your kernel should be preemtable that
means processor should be given to other process when timeslice
expires. But for this process should not hold any lock. As when
spinlocks are help by code, actually we disable the preemption till
the time we do not release spinlock. So code inbetween spin_lock() and
spin_unlock() is not preemptable.
Please so post your experimental code once again.
Gaurav
> > and everything looks fine.
>
> hm, strange...what is the relation between printk(), pid and spin lock....
>
> let's do it a bit different, how about this?
>
> pid_t mypid;
> mypid = current->pid;
> printk("this is process %d\n",mypid);
>
> does it work?
>
> > without spin lock, something goes wrong, It looks someone disable
> > interrupt and I tried to enable interrupt but it didn't work.
> again....very strange. Your kernel thread PID should be static, right?
>
> regards
>
> Mulyadi
>
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>
>
--
--
-Gaurav
Email: gauravd.chd@xxxxxxxxx
---------------------------------
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