From 14a40ffccd6163bbcd1d6f32b28a88ffe6149fc6 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 19 Mar 2013 13:45:20 -0700 Subject: 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 Acked-by: Ingo Molnar Reviewed-by: Lai Jiangshan Cc: Peter Zijlstra Cc: Thomas Gleixner --- kernel/cgroup.c | 4 ++-- kernel/cpuset.c | 16 ++++++++-------- kernel/kthread.c | 2 +- kernel/sched/core.c | 9 ++++----- kernel/workqueue.c | 10 +++------- 5 files changed, 18 insertions(+), 23 deletions(-) (limited to 'kernel') 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); } -- cgit v1.2.3-18-g5258