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

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

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