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

J. Bruce Fields
2020-07-07T15:33:06Z

NACK to this and following patch.--b.

On Tue, Jul 07, 2020 at 05:17:15PM +0200, Greg Kroah-Hartman wrote:
> 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
>
>
>