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authorTejun Heo <tj@kernel.org>2013-03-19 13:45:20 -0700
committerTejun Heo <tj@kernel.org>2013-03-19 13:45:20 -0700
commit14a40ffccd6163bbcd1d6f32b28a88ffe6149fc6 (patch)
treeeb61e5bf7b64c3e67f3e33fe6b07fde4ee1d4d43 /kernel
parent2e109a2855bf6cf675a8b74dbd89b6492e8def42 (diff)
downloadlinaro-lsk-14a40ffccd6163bbcd1d6f32b28a88ffe6149fc6.tar.gz
sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
PF_THREAD_BOUND was originally used to mark kernel threads which were bound to a specific CPU using kthread_bind() and a task with the flag set allows cpus_allowed modifications only to itself. Workqueue is currently abusing it to prevent userland from meddling with cpus_allowed of workqueue workers. What we need is a flag to prevent userland from messing with cpus_allowed of certain kernel tasks. In kernel, anyone can (incorrectly) squash the flag, and, for worker-type usages, restricting cpus_allowed modification to the task itself doesn't provide meaningful extra proection as other tasks can inject work items to the task anyway. This patch replaces PF_THREAD_BOUND with PF_NO_SETAFFINITY. sched_setaffinity() checks the flag and return -EINVAL if set. set_cpus_allowed_ptr() is no longer affected by the flag. This will allow simplifying workqueue worker CPU affinity management. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup.c4
-rw-r--r--kernel/cpuset.c16
-rw-r--r--kernel/kthread.c2
-rw-r--r--kernel/sched/core.c9
-rw-r--r--kernel/workqueue.c10
5 files changed, 18 insertions, 23 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a32f9432666..3852d926322 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2224,11 +2224,11 @@ retry_find_task:
tsk = tsk->group_leader;
/*
- * Workqueue threads may acquire PF_THREAD_BOUND and become
+ * Workqueue threads may acquire PF_NO_SETAFFINITY and become
* trapped in a cpuset, or RT worker may be born in a cgroup
* with no rt_runtime allocated. Just say no.
*/
- if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
+ if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
ret = -EINVAL;
rcu_read_unlock();
goto out_unlock_cgroup;
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4f9dfe43ecb..f22e9479270 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1388,16 +1388,16 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
cgroup_taskset_for_each(task, cgrp, tset) {
/*
- * 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.
+ * Kthreads which disallow setaffinity shouldn't be moved
+ * to a new cpuset; we don't want to 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.
*/
ret = -EINVAL;
- if (task->flags & PF_THREAD_BOUND)
+ if (task->flags & PF_NO_SETAFFINITY)
goto out_unlock;
ret = security_task_setscheduler(task);
if (ret)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 691dc2ef9ba..a2fbbb782ba 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -260,7 +260,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu)
{
/* It's safe because the task is inactive. */
do_set_cpus_allowed(p, cpumask_of(cpu));
- p->flags |= PF_THREAD_BOUND;
+ p->flags |= PF_NO_SETAFFINITY;
}
/**
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f12624a393..23606ee961b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4126,6 +4126,10 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
get_task_struct(p);
rcu_read_unlock();
+ if (p->flags & PF_NO_SETAFFINITY) {
+ retval = -EINVAL;
+ goto out_put_task;
+ }
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
retval = -ENOMEM;
goto out_put_task;
@@ -4773,11 +4777,6 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
goto out;
}
- if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
- ret = -EINVAL;
- goto out;
- }
-
do_set_cpus_allowed(p, new_mask);
/* Can the task run on the task's current CPU? If so, we're done */
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 969be0b7207..39a591f65b0 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1757,12 +1757,8 @@ static struct worker *create_worker(struct worker_pool *pool)
set_user_nice(worker->task, pool->attrs->nice);
set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
- /*
- * %PF_THREAD_BOUND is used to prevent userland from meddling with
- * cpumask of workqueue workers. This is an abuse. We need
- * %PF_NO_SETAFFINITY.
- */
- worker->task->flags |= PF_THREAD_BOUND;
+ /* prevent userland from meddling with cpumask of workqueue workers */
+ worker->task->flags |= PF_NO_SETAFFINITY;
/*
* The caller is responsible for ensuring %POOL_DISASSOCIATED
@@ -3876,7 +3872,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
}
wq->rescuer = rescuer;
- rescuer->task->flags |= PF_THREAD_BOUND;
+ rescuer->task->flags |= PF_NO_SETAFFINITY;
wake_up_process(rescuer->task);
}