Re: [Experimental CPU Hotplug PATCH] - Move migrate_all_tasks to CPU_DEAD handling

[Rusty Russell <rusty@rustcorp.com.au>]

On Thu, 2004-04-08 at 00:17, Srivatsa Vaddagiri wrote:
> On Wed, Apr 07, 2004 at 03:32:12PM +1000, Rusty Russell wrote:
> > But other tasks can do a getaffinity() on it and see the wrong affinity.
> > Probably not a big issue.
> 
> hmm .. the fact that getaffinity reads the cpus_allowed mask w/o doing
> lock_cpu_hotplug makes it already racy wrt setaffinity?

But that's OK: that's a user race.  It's like reading a file at the same
time as writing it.

> Maybe it needs to take CPU hotplug sem before it reads the mask?

Yes, taking it in both syscalls would work, too.

> I would like to run my stress tests for longer time before I send it
> for inclusion (i would be on vacation till next tuesday ..so maybe i will send
> in the patch after that!)

Thanks.  BTW, can you take a look at the FIXME: in xics.c and change it
to be dynamic.  Joel is having trouble proving it's a problem, and yet
Anton assures me that ioremap is needed, so CPUs not present at boot
which are brought in should be failing...

Thanks!
Rusty.
-- 
Anyone who quotes me in their signature is an idiot -- Rusty Russell