A few code details (still working on more substantive reply):

+       /* An isolated cpuset has to be exclusive */
+       if ((is_cpu_isolated(trial) && !is_cpu_exclusive(cur)) 
+          || (!is_cpu_exclusive(trial) && is_cpu_isolated(cur)))
+               return -EINVAL;

Is the above code equivalant to what the comment states:

        if (is_cpu_isolated(trial) <= is_cpu_exclusive(trial))
                return -EINVAL;

+       t = old_parent = *par;
+       cpus_or(all_map, cs->cpus_allowed, cs->isolated_map);
+
+       /* If cpuset empty or top_cpuset, return */
+        if (cpus_empty(all_map) || par == NULL)
+                return;

If the (par == NULL) check succeeds, then perhaps the earlier (*par)
dereference will have oopsed first?

+       struct cpuset *par = cs->parent, t, old_parent;

Looks like 't' was chosen to be a one-char variable name, to keep some
lines below within 80 columns.  I'd do the same myself.  But this leaves
a non-symmetrical naming pattern for the new and old parent cpuset values.

Perhaps the following would work better?

        struct cpuset *parptr;
        struct cpuset o, n;     /* old and new parent cpuset values */

+static void update_cpu_domains(struct cpuset *cs, cpumask_t old_map)

Could old_map be passed as a (const cpumask_t *)?  The stack space of
this code, just for cpumask_t's (see the old and new above) is getting
large for (really) big systems.

+       /* Make the change */
+       par->cpus_allowed = t.cpus_allowed;
+       par->isolated_map = t.isolated_map;

Why don't you need to propogate upward this change to the parents
cpus_allowed and isolated_map?  If a parents isolated_map grows (or
shrinks), doesn't that affect every ancestor, all the way to the top
cpuset?

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <[EMAIL PROTECTED]> 1.650.933.1373, 
1.925.600.0401
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