diff options
author | Tejun Heo <tj@kernel.org> | 2013-03-19 20:45:20 (GMT) |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2013-03-19 20:45:20 (GMT) |
commit | 14a40ffccd6163bbcd1d6f32b28a88ffe6149fc6 (patch) | |
tree | eb61e5bf7b64c3e67f3e33fe6b07fde4ee1d4d43 /kernel | |
parent | 2e109a2855bf6cf675a8b74dbd89b6492e8def42 (diff) | |
download | linux-fsl-qoriq-14a40ffccd6163bbcd1d6f32b28a88ffe6149fc6.tar.xz |
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.c | 4 | ||||
-rw-r--r-- | kernel/cpuset.c | 16 | ||||
-rw-r--r-- | kernel/kthread.c | 2 | ||||
-rw-r--r-- | kernel/sched/core.c | 9 | ||||
-rw-r--r-- | kernel/workqueue.c | 10 |
5 files changed, 18 insertions, 23 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index a32f943..3852d92 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 4f9dfe4..f22e947 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 691dc2e..a2fbbb7 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 7f12624..23606ee 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 969be0b..39a591f 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); } |