cpusets: prevent PF_THREAD_BOUND tasks from attaching to non-root cpusets (6d7b2f5f) · Commits · 戴 / test

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>

kernel/cpuset.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -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,

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