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cpusets: prevent PF_THREAD_BOUND tasks from attaching to non-root cpusets 

Kthreads that have the PF_THREAD_BOUND bit set in their flags are bound to a
specific cpu.  Thus, their set of allowed cpus shall not change.

This patch prevents such threads from attaching to non-root cpusets.  They do
not have mempolicies that restrict them to a subset of system nodes and, since
their cpumask may never change, they cannot use any of the features of
cpusets.

The tasks will forever be a member of the root cpuset and will be returned
when listing the tasks attached to that cpuset.

Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2009-04-02 16:57:57 -07:00 committed by Linus Torvalds
parent db7f47cf48
commit 6d7b2f5f9e
1 changed files with 11 additions and 8 deletions
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19
kernel/cpuset.c
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@ -1342,19 +1342,22 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct task_struct *tsk)
{
struct cpuset *cs = cgroup_cs(cont);
int ret = 0;
if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC;
if (tsk->flags & PF_THREAD_BOUND) {
mutex_lock(&callback_mutex);
if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed))
ret = -EINVAL;
mutex_unlock(&callback_mutex);
}
/*
* Kthreads bound to specific cpus cannot be moved to a new cpuset; we
* cannot change their cpu affinity and isolating such threads by their
* set of allowed nodes is unnecessary. Thus, cpusets are not
* applicable for such threads. This prevents checking for success of
* set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
* be changed.
*/
if (tsk->flags & PF_THREAD_BOUND)
return -EINVAL;
return ret < 0 ? ret : security_task_setscheduler(tsk, 0, NULL);
return security_task_setscheduler(tsk, 0, NULL);
}
static void cpuset_attach(struct cgroup_subsys *ss,