kthread: save thread function

It's handy to keep the kthread_fn just as a unique cookie to identify
classes of kthreads.  E.g. if you can verify that a given task is
running your thread_fn, then you may know what sort of type kthread_data
points to.

We'll use this in nfsd to pass some information into the vfs.  Note it
will need kthread_data() exported too.

Original-patch-by: Tejun Heo <tj@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 8bbcaad7ef0f4ed684a5177fbf6062029b868616..c2a274b79c429e3ba137dddb85b51a154d9d4a6a 100644 (file)
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -57,6 +57,7 @@ bool kthread_should_stop(void);
 bool kthread_should_park(void);
 bool __kthread_should_park(struct task_struct *k);
 bool kthread_freezable_should_stop(bool *was_frozen);
+void *kthread_func(struct task_struct *k);
 void *kthread_data(struct task_struct *k);
 void *kthread_probe_data(struct task_struct *k);
 int kthread_park(struct task_struct *k);

diff --git a/kernel/kthread.c b/kernel/kthread.c
index bfbfa481be3a56e3efb7641eb47fdd8f6a274c32..b84fc7eec0358e94047cc182441035e5fd2cea00 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -46,6 +46,7 @@ struct kthread_create_info
 struct kthread {
        unsigned long flags;
        unsigned int cpu;
+       int (*threadfn)(void *);
        void *data;
        struct completion parked;
        struct completion exited;
@@ -152,6 +153,20 @@ bool kthread_freezable_should_stop(bool *was_frozen)
 }
 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
 
+/**
+ * kthread_func - return the function specified on kthread creation
+ * @task: kthread task in question
+ *
+ * Returns NULL if the task is not a kthread.
+ */
+void *kthread_func(struct task_struct *task)
+{
+       if (task->flags & PF_KTHREAD)
+               return to_kthread(task)->threadfn;
+       return NULL;
+}
+EXPORT_SYMBOL_GPL(kthread_func);
+
 /**
  * kthread_data - return data value specified on kthread creation
  * @task: kthread task in question
@@ -164,6 +179,7 @@ void *kthread_data(struct task_struct *task)
 {
        return to_kthread(task)->data;
 }
+EXPORT_SYMBOL_GPL(kthread_data);
 
 /**
  * kthread_probe_data - speculative version of kthread_data()
@@ -244,6 +260,7 @@ static int kthread(void *_create)
                do_exit(-ENOMEM);
        }
 
+       self->threadfn = threadfn;
        self->data = data;
        init_completion(&self->exited);
        init_completion(&self->parked);