Re: 2.6.21-rc7-mm1: BUG_ON in kthread_bind during _cpu_down

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 26 Apr 2007 18:28:38 +0530
Gautham R Shenoy <ego@in.ibm.com> wrote:

> I just checked with Vatsa if there was any subtle reason why they
> had put in the kthread_bind() in cpu.c. Vatsa cannot seem to recollect
> any and I can't see any. So let us just remove the kthread_bind.
> 
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
> ---
>  kernel/cpu.c |    4 ----
>  1 files changed, 4 deletions(-)
> 
> Index: linux-2.6.21-rc7/kernel/cpu.c
> ===================================================================
> --- linux-2.6.21-rc7.orig/kernel/cpu.c
> +++ linux-2.6.21-rc7/kernel/cpu.c
> @@ -176,10 +176,6 @@ static int _cpu_down(unsigned int cpu, i
>  	/* This actually kills the CPU. */
>  	__cpu_die(cpu);
>  
> -	/* Move it here so it can run. */
> -	kthread_bind(p, get_cpu());
> -	put_cpu();
> -
>  	/* CPU is completely dead: tell everyone.  Too late to complain. */
>  	if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
>  				    hcpu) == NOTIFY_BAD)

So I cooked up a changelog and queued up the diff.  But I have an uneasy
feeling that things are getting a bit close to guesswork here.

We have a huge amount of change pending in the kthread/workqueue/freezer
area, partly because I decided not to merge most of the workqueue changes
into 2.6.21.

It'd be good if people could take some time to sit down and re-review the
code which we presently have.  I plan on sending it all off for 2.6.22 and
there might be some glitches but it seems to have a good track record so
far.