Eric Lee / linux-smarc-t335x-v3.2

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Commit 6d7b2f5f9e88902b19f91d0c8a7ef58a5455f1a2

Authored by David Rientjes
Committed by Linus Torvalds
1 parent db7f47cf48
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

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>

Showing 1 changed file with 11 additions and 8 deletions Side-by-side Diff

... ... @@ -1342,19 +1342,22 @@
1342 1342 struct cgroup *cont, struct task_struct *tsk)
1343 1343 {
1344 1344 struct cpuset *cs = cgroup_cs(cont);
1345   - int ret = 0;
1346 1345  
1347 1346 if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
1348 1347 return -ENOSPC;
1349 1348  
1350   - if (tsk->flags & PF_THREAD_BOUND) {
1351   - mutex_lock(&callback_mutex);
1352   - if (!cpumask_equal(&tsk->cpus_allowed, cs->cpus_allowed))
1353   - ret = -EINVAL;
1354   - mutex_unlock(&callback_mutex);
1355   - }
  1349 + /*
  1350 + * Kthreads bound to specific cpus cannot be moved to a new cpuset; we
  1351 + * cannot change their cpu affinity and isolating such threads by their
  1352 + * set of allowed nodes is unnecessary. Thus, cpusets are not
  1353 + * applicable for such threads. This prevents checking for success of
  1354 + * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
  1355 + * be changed.
  1356 + */
  1357 + if (tsk->flags & PF_THREAD_BOUND)
  1358 + return -EINVAL;
1356 1359  
1357   - return ret < 0 ? ret : security_task_setscheduler(tsk, 0, NULL);
  1360 + return security_task_setscheduler(tsk, 0, NULL);
1358 1361 }
1359 1362  
1360 1363 static void cpuset_attach(struct cgroup_subsys *ss,