Commit 6d7b2f5f authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds

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: default avatarDavid Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent db7f47cf
...@@ -1342,19 +1342,22 @@ static int cpuset_can_attach(struct cgroup_subsys *ss, ...@@ -1342,19 +1342,22 @@ static int cpuset_can_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct task_struct *tsk) struct cgroup *cont, struct task_struct *tsk)
{ {
struct cpuset *cs = cgroup_cs(cont); struct cpuset *cs = cgroup_cs(cont);
int ret = 0;
if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)) if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC; return -ENOSPC;
if (tsk->flags & PF_THREAD_BOUND) { /*
mutex_lock(&callback_mutex); * Kthreads bound to specific cpus cannot be moved to a new cpuset; we
if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed)) * cannot change their cpu affinity and isolating such threads by their
ret = -EINVAL; * set of allowed nodes is unnecessary. Thus, cpusets are not
mutex_unlock(&callback_mutex); * 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, static void cpuset_attach(struct cgroup_subsys *ss,
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment