[PATCH] linux/kthread.h: remove unused macros

[PATCH] linux/kthread.h: remove unused macros

[Rasmus Villemoes]

Ever since these macros were introduced in commit b56c0d8937e6
("kthread: implement kthread_worker"), there has been precisely one
user (commit 4d115420707a, "NVMe: Async IO queue deletion"), and that
user went away in 2016 with db3cbfff5bcc ("NVMe: IO queue deletion
re-write").

Apart from being unused, these macros are also awkward to use (which
may contribute to them not being used): Having a way to statically (or
on-stack) allocating the storage for the struct kthread_worker itself
doesn't help much, since obviously one needs to have some code for
actually _spawning_ the worker thread, which must have error
checking. And these days we have the kthread_create_worker() interface
which both allocates the struct kthread_worker and spawns the kthread.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 include/linux/kthread.h | 22 ----------------------
 1 file changed, 22 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 3df4ea04716f..de5d75bafd66 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -141,12 +141,6 @@ struct kthread_delayed_work {
 	struct timer_list timer;
 };
 
-#define KTHREAD_WORKER_INIT(worker)	{				\
-	.lock = __RAW_SPIN_LOCK_UNLOCKED((worker).lock),		\
-	.work_list = LIST_HEAD_INIT((worker).work_list),		\
-	.delayed_work_list = LIST_HEAD_INIT((worker).delayed_work_list),\
-	}
-
 #define KTHREAD_WORK_INIT(work, fn)	{				\
 	.node = LIST_HEAD_INIT((work).node),				\
 	.func = (fn),							\
@@ -158,9 +152,6 @@ struct kthread_delayed_work {
 				     TIMER_IRQSAFE),			\
 	}
 
-#define DEFINE_KTHREAD_WORKER(worker)					\
-	struct kthread_worker worker = KTHREAD_WORKER_INIT(worker)
-
 #define DEFINE_KTHREAD_WORK(work, fn)					\
 	struct kthread_work work = KTHREAD_WORK_INIT(work, fn)
 
@@ -168,19 +159,6 @@ struct kthread_delayed_work {
 	struct kthread_delayed_work dwork =				\
 		KTHREAD_DELAYED_WORK_INIT(dwork, fn)
 
-/*
- * kthread_worker.lock needs its own lockdep class key when defined on
- * stack with lockdep enabled.  Use the following macros in such cases.
- */
-#ifdef CONFIG_LOCKDEP
-# define KTHREAD_WORKER_INIT_ONSTACK(worker)				\
-	({ kthread_init_worker(&worker); worker; })
-# define DEFINE_KTHREAD_WORKER_ONSTACK(worker)				\
-	struct kthread_worker worker = KTHREAD_WORKER_INIT_ONSTACK(worker)
-#else
-# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) DEFINE_KTHREAD_WORKER(worker)
-#endif
-
 extern void __kthread_init_worker(struct kthread_worker *worker,
 			const char *name, struct lock_class_key *key);
 
-- 
2.31.1

Re: [PATCH] linux/kthread.h: remove unused macros

[Tejun Heo]

On Mon, Mar 14, 2022 at 03:53:42PM +0100, Rasmus Villemoes wrote:
> Ever since these macros were introduced in commit b56c0d8937e6
> ("kthread: implement kthread_worker"), there has been precisely one
> user (commit 4d115420707a, "NVMe: Async IO queue deletion"), and that
> user went away in 2016 with db3cbfff5bcc ("NVMe: IO queue deletion
> re-write").
> 
> Apart from being unused, these macros are also awkward to use (which
> may contribute to them not being used): Having a way to statically (or
> on-stack) allocating the storage for the struct kthread_worker itself
> doesn't help much, since obviously one needs to have some code for
> actually _spawning_ the worker thread, which must have error
> checking. And these days we have the kthread_create_worker() interface
> which both allocates the struct kthread_worker and spawns the kthread.
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH] linux/kthread.h: remove unused macros

[Petr Mladek]

On Mon 2022-03-14 15:53:42, Rasmus Villemoes wrote:
> Ever since these macros were introduced in commit b56c0d8937e6
> ("kthread: implement kthread_worker"), there has been precisely one
> user (commit 4d115420707a, "NVMe: Async IO queue deletion"), and that
> user went away in 2016 with db3cbfff5bcc ("NVMe: IO queue deletion
> re-write").
> 
> Apart from being unused, these macros are also awkward to use (which
> may contribute to them not being used): Having a way to statically (or
> on-stack) allocating the storage for the struct kthread_worker itself
> doesn't help much, since obviously one needs to have some code for
> actually _spawning_ the worker thread, which must have error
> checking. And these days we have the kthread_create_worker() interface
> which both allocates the struct kthread_worker and spawns the kthread.
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Makes sense.

Acked-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr