The patch titled
Subject: cpusets, cgroups: disallow attaching kthreadd
has been removed from the -mm tree. Its filename was
cpusets-cgroups-disallow-attaching-kthreadd.patch
This patch was dropped because other changes were merged, which wrecked this patch
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Mike Galbraith <efault@xxxxxx>
Subject: cpusets, cgroups: disallow attaching kthreadd
Allowing kthreadd to be moved to a non-root group makes no sense, it being
a global resource, and needlessly leads unsuspecting users toward trouble.
1. An RT workqueue worker thread spawned in a task group with no
rt_runtime allocated is not schedulable. Simple user error, but
harmful to the box.
2. A worker thread which acquires PF_THREAD_BOUND can never leave a
cpuset, rendering the cpuset immortal.
Save the user some unexpected trouble, just say no.
Signed-off-by: Mike Galbraith <efault@xxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Paul Menage <paul@xxxxxxxxxxxxxx>
Cc: Tejun Heo <htejun@xxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cpuset.c | 7 +++++--
kernel/sched/core.c | 9 +++++++++
2 files changed, 14 insertions(+), 2 deletions(-)
diff -puN kernel/cpuset.c~cpusets-cgroups-disallow-attaching-kthreadd kernel/cpuset.c
--- a/kernel/cpuset.c~cpusets-cgroups-disallow-attaching-kthreadd
+++ a/kernel/cpuset.c
@@ -59,6 +59,7 @@
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/cgroup.h>
+#include <linux/kthread.h>
/*
* Workqueue for cpuset related tasks.
@@ -1417,9 +1418,11 @@ static int cpuset_can_attach(struct cgro
* 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.
+ * cpus_allowed may be changed. We also disallow attaching
+ * kthreadd, to prevent its child from becoming trapped should
+ * it then acquire PF_THREAD_BOUND.
*/
- if (task->flags & PF_THREAD_BOUND)
+ if (task->flags & PF_THREAD_BOUND || task == kthreadd_task)
return -EINVAL;
if ((ret = security_task_setscheduler(task)))
return ret;
diff -puN kernel/sched/core.c~cpusets-cgroups-disallow-attaching-kthreadd kernel/sched/core.c
--- a/kernel/sched/core.c~cpusets-cgroups-disallow-attaching-kthreadd
+++ a/kernel/sched/core.c
@@ -71,6 +71,7 @@
#include <linux/ftrace.h>
#include <linux/slab.h>
#include <linux/init_task.h>
+#include <linux/kthread.h>
#include <asm/tlb.h>
#include <asm/irq_regs.h>
@@ -7535,6 +7536,14 @@ static int cpu_cgroup_can_attach(struct
struct task_struct *task;
cgroup_taskset_for_each(task, cgrp, tset) {
+ /*
+ * kthreadd can fork workers for an RT workqueue in a cgroup
+ * which may or may not have rt_runtime allocated. Just say no,
+ * as attaching a global resource to a non-root group doesn't
+ * make any sense anyway.
+ */
+ if (task == kthreadd_task)
+ return -EINVAL;
#ifdef CONFIG_RT_GROUP_SCHED
if (!sched_rt_can_attach(cgroup_tg(cgrp), task))
return -EINVAL;
_
Patches currently in -mm which might be from efault@xxxxxx are
origin.patch
linux-next.patch
ipc-semc-alternatives-to-preempt_disable.patch
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