[PATCH 5.7 070/112] kthread: save thread function

Greg Kroah-Hartman
2020-07-07T15:25:16Z

From: J. Bruce Fields <bfields@redhat.com>

[ Upstream commit 52782c92ac85c4e393eb4a903a62e6c24afa633f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/kthread.h | 1 +
kernel/kthread.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 8bbcaad7ef0f4..c2a274b79c429 100644
--- 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 bfbfa481be3a5..b84fc7eec0358 100644
--- 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);
--
2.25.1