* [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
[not found] <20130308204518.GR14556@mtj.dyndns.org>
@ 2013-03-14 22:55 ` Tejun Heo
2013-03-18 9:41 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Tejun Heo @ 2013-03-14 22:55 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Peter Zijlstra, Thomas Gleixner, Andrew Morton, linux-kernel
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>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
Reposted because the original posting forgot to cc lkml.
Thanks.
include/linux/sched.h | 2 +-
kernel/cgroup.c | 4 ++--
kernel/cpuset.c | 16 ++++++++--------
kernel/kthread.c | 2 +-
kernel/sched/core.c | 9 ++++-----
kernel/workqueue.c | 6 +++---
6 files changed, 19 insertions(+), 20 deletions(-)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1793,7 +1793,7 @@ extern void thread_group_cputime_adjuste
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
-#define PF_THREAD_BOUND 0x04000000 /* Thread bound to specific cpu */
+#define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_allowed */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
#define PF_MUTEX_TESTER 0x20000000 /* Thread belongs to the rt mutex tester */
--- 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;
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1388,16 +1388,16 @@ static int cpuset_can_attach(struct cgro
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)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -260,7 +260,7 @@ static void __kthread_bind(struct task_s
{
/* 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;
}
/**
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4126,6 +4126,10 @@ long sched_setaffinity(pid_t pid, const
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;
@@ -4772,11 +4776,6 @@ int set_cpus_allowed_ptr(struct task_str
ret = -EINVAL;
goto out;
}
-
- if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
- ret = -EINVAL;
- goto out;
- }
do_set_cpus_allowed(p, new_mask);
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1741,12 +1741,12 @@ static struct worker *create_worker(stru
* above the flag definition for details.
*
* As an unbound worker may later become a regular one if CPU comes
- * online, make sure every worker has %PF_THREAD_BOUND set.
+ * online, make sure every worker has %PF_NO_SETAFFINITY set.
*/
if (!(pool->flags & POOL_DISASSOCIATED)) {
kthread_bind(worker->task, pool->cpu);
} else {
- worker->task->flags |= PF_THREAD_BOUND;
+ worker->task->flags |= PF_NO_SETAFFINITY;
worker->flags |= WORKER_UNBOUND;
}
@@ -3219,7 +3219,7 @@ struct workqueue_struct *__alloc_workque
if (IS_ERR(rescuer->task))
goto err;
- rescuer->task->flags |= PF_THREAD_BOUND;
+ rescuer->task->flags |= PF_NO_SETAFFINITY;
wake_up_process(rescuer->task);
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
2013-03-14 22:55 ` [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY Tejun Heo
@ 2013-03-18 9:41 ` Ingo Molnar
2013-03-18 16:47 ` Tejun Heo
0 siblings, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2013-03-18 9:41 UTC (permalink / raw)
To: Tejun Heo
Cc: Ingo Molnar, Peter Zijlstra, Thomas Gleixner, Andrew Morton,
linux-kernel
* Tejun Heo <tj@kernel.org> wrote:
> 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.
Acked-by: Ingo Molnar <mingo@kernel.org>
I suspect you want to carry this in the workqueue tree, to enable those
extra simplifications?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
2013-03-18 9:41 ` Ingo Molnar
@ 2013-03-18 16:47 ` Tejun Heo
2013-03-19 20:48 ` Tejun Heo
0 siblings, 1 reply; 4+ messages in thread
From: Tejun Heo @ 2013-03-18 16:47 UTC (permalink / raw)
To: Ingo Molnar
Cc: Ingo Molnar, Peter Zijlstra, Thomas Gleixner, Andrew Morton,
linux-kernel
Hello,
On Mon, Mar 18, 2013 at 10:41:40AM +0100, Ingo Molnar wrote:
> > 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.
>
> Acked-by: Ingo Molnar <mingo@kernel.org>
>
> I suspect you want to carry this in the workqueue tree, to enable those
> extra simplifications?
Yeah, I was planning to pull from one of the -tip branches but if I
can carry it through the workqueue tree it would be simpler. Would
that be okay?
Thanks.
--
tejun
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY
2013-03-18 16:47 ` Tejun Heo
@ 2013-03-19 20:48 ` Tejun Heo
0 siblings, 0 replies; 4+ messages in thread
From: Tejun Heo @ 2013-03-19 20:48 UTC (permalink / raw)
To: Ingo Molnar
Cc: Ingo Molnar, Peter Zijlstra, Thomas Gleixner, Andrew Morton,
linux-kernel
On Mon, Mar 18, 2013 at 09:47:15AM -0700, Tejun Heo wrote:
> Hello,
>
> On Mon, Mar 18, 2013 at 10:41:40AM +0100, Ingo Molnar wrote:
> > > 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.
> >
> > Acked-by: Ingo Molnar <mingo@kernel.org>
> >
> > I suspect you want to carry this in the workqueue tree, to enable those
> > extra simplifications?
>
> Yeah, I was planning to pull from one of the -tip branches but if I
> can carry it through the workqueue tree it would be simpler. Would
> that be okay?
Applying to wq/for-3.10 w/ the rebinding cleanup. Holler if this
should be routed differently.
Thanks!
--
tejun
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-03-14 22:55 ` [PATCH REPOST v3.9-rc1] sched: replace PF_THREAD_BOUND with PF_NO_SETAFFINITY Tejun Heo
2013-03-18 9:41 ` Ingo Molnar
2013-03-18 16:47 ` Tejun Heo
2013-03-19 20:48 ` Tejun Heo
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