Re: [PATCH 02/12] workqueue: disallow set_cpus_allowed_ptr() from work item
On Thu, Sep 27, 2012 at 01:20:33AM +0800, Lai Jiangshan wrote: > workers depend on local-wake-up, if a work function change its CPU, it will > corrupt workqueue, disallow this behavior. > > When set_cpus_allowed_ptr() is called from workqueue.c in worker_thread(), > we clear the PF_WQ_WORKER before set_cpus_allowed_ptr() and set it back > after. (rescuer thread has no PF_WQ_WORKER, skip this behavior) > > It prevents other/future BUGs like > https://bugzilla.kernel.org/show_bug.cgi?id=47301. Hmmm... maybe. We better clear up PF_THREAD_BOUND semantics first tho. I think the two possible choices are, * Don't allow set_cpus_allowed_ptr() at all and make the caller responsible for turning it off if it explicitly wants to change cpus_allowed. * Don't allow changing affinity from userland. Peter, Thomas? -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 02/12] workqueue: disallow set_cpus_allowed_ptr() from work item
workers depend on local-wake-up, if a work function change its CPU, it will
corrupt workqueue, disallow this behavior.
When set_cpus_allowed_ptr() is called from workqueue.c in worker_thread(),
we clear the PF_WQ_WORKER before set_cpus_allowed_ptr() and set it back
after. (rescuer thread has no PF_WQ_WORKER, skip this behavior)
It prevents other/future BUGs like
https://bugzilla.kernel.org/show_bug.cgi?id=47301.
CC: tangchen
Signed-off-by: Lai Jiangshan
---
kernel/sched/core.c |8 +---
kernel/workqueue.c | 10 +-
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d325c4b..355d3cc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5187,9 +5187,11 @@ 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;
+ if (unlikely(p->flags & PF_THREAD_BOUND)) {
+ if (WARN_ON_ONCE(p->flags & PF_WQ_WORKER) || p != current) {
+ ret = -EINVAL;
+ goto out;
+ }
}
do_set_cpus_allowed(p, new_mask);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ec882a6..c55884d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1600,6 +1600,7 @@ __acquires(>lock)
struct global_cwq *gcwq = worker->pool->gcwq;
struct task_struct *task = worker->task;
+ BUG_ON(task != current);
while (true) {
/*
* The following call may fail, succeed or succeed
@@ -1607,9 +1608,16 @@ __acquires(>lock)
* it races with cpu hotunplug operation. Verify
* against GCWQ_DISASSOCIATED.
*/
- if (!(gcwq->flags & GCWQ_DISASSOCIATED))
+ if (!(gcwq->flags & GCWQ_DISASSOCIATED)) {
+ if (!(worker->flags & WORKER_RESCUER))
+ task->flags &= ~PF_WQ_WORKER;
+
set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
+ if (!(worker->flags & WORKER_RESCUER))
+ task->flags |= PF_WQ_WORKER;
+ }
+
spin_lock_irq(>lock);
if (gcwq->flags & GCWQ_DISASSOCIATED)
return false;
--
1.7.7.6
--
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Please read the FAQ at http://www.tux.org/lkml/
[PATCH 02/12] workqueue: disallow set_cpus_allowed_ptr() from work item
workers depend on local-wake-up, if a work function change its CPU, it will
corrupt workqueue, disallow this behavior.
When set_cpus_allowed_ptr() is called from workqueue.c in worker_thread(),
we clear the PF_WQ_WORKER before set_cpus_allowed_ptr() and set it back
after. (rescuer thread has no PF_WQ_WORKER, skip this behavior)
It prevents other/future BUGs like
https://bugzilla.kernel.org/show_bug.cgi?id=47301.
CC: tangchen tangc...@cn.fujitsu.com
Signed-off-by: Lai Jiangshan la...@cn.fujitsu.com
---
kernel/sched/core.c |8 +---
kernel/workqueue.c | 10 +-
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d325c4b..355d3cc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5187,9 +5187,11 @@ 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;
+ if (unlikely(p-flags PF_THREAD_BOUND)) {
+ if (WARN_ON_ONCE(p-flags PF_WQ_WORKER) || p != current) {
+ ret = -EINVAL;
+ goto out;
+ }
}
do_set_cpus_allowed(p, new_mask);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ec882a6..c55884d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1600,6 +1600,7 @@ __acquires(gcwq-lock)
struct global_cwq *gcwq = worker-pool-gcwq;
struct task_struct *task = worker-task;
+ BUG_ON(task != current);
while (true) {
/*
* The following call may fail, succeed or succeed
@@ -1607,9 +1608,16 @@ __acquires(gcwq-lock)
* it races with cpu hotunplug operation. Verify
* against GCWQ_DISASSOCIATED.
*/
- if (!(gcwq-flags GCWQ_DISASSOCIATED))
+ if (!(gcwq-flags GCWQ_DISASSOCIATED)) {
+ if (!(worker-flags WORKER_RESCUER))
+ task-flags = ~PF_WQ_WORKER;
+
set_cpus_allowed_ptr(task, get_cpu_mask(gcwq-cpu));
+ if (!(worker-flags WORKER_RESCUER))
+ task-flags |= PF_WQ_WORKER;
+ }
+
spin_lock_irq(gcwq-lock);
if (gcwq-flags GCWQ_DISASSOCIATED)
return false;
--
1.7.7.6
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 02/12] workqueue: disallow set_cpus_allowed_ptr() from work item
On Thu, Sep 27, 2012 at 01:20:33AM +0800, Lai Jiangshan wrote: workers depend on local-wake-up, if a work function change its CPU, it will corrupt workqueue, disallow this behavior. When set_cpus_allowed_ptr() is called from workqueue.c in worker_thread(), we clear the PF_WQ_WORKER before set_cpus_allowed_ptr() and set it back after. (rescuer thread has no PF_WQ_WORKER, skip this behavior) It prevents other/future BUGs like https://bugzilla.kernel.org/show_bug.cgi?id=47301. Hmmm... maybe. We better clear up PF_THREAD_BOUND semantics first tho. I think the two possible choices are, * Don't allow set_cpus_allowed_ptr() at all and make the caller responsible for turning it off if it explicitly wants to change cpus_allowed. * Don't allow changing affinity from userland. Peter, Thomas? -- tejun -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
