linux-kernel - [PATCH 2/5] kmod: Use system_unbound

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Date:	Thu,  9 Jul 2015 20:07:14 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 2/5] kmod: Use system_unbound_wq instead of khelper

We need to launch the usermodehelper kernel threads with the widest
affinity and this is why we have khelper for. This workqueue has unbound
properties and thus a wide affinity inherited by all its children.

Now khelper also has special properties that we aren't much interested
in: ordered and singlethread. There is really no need about ordering as
all we do is creating kernel threads. This can be done concurrently.
And singlethread is a useless limitation as well.

The workqueue engine already proposes generic unbound workqueues that
don't share these useless properties and handle well parallel jobs.

Lets just use them.

Suggested-by: Oleg Nesterov <oleg@...hat.com>
Cc: Rik van Riel <riel@...hat.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Lameter <cl@...ux.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 include/linux/kmod.h |  2 --
 init/main.c          |  1 -
 kernel/kmod.c        | 12 ++----------
 3 files changed, 2 insertions(+), 13 deletions(-)

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 0555cc6..fcfd2bf 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -85,8 +85,6 @@ enum umh_disable_depth {
 	UMH_DISABLED,
 };
 
-extern void usermodehelper_init(void);
-
 extern int __usermodehelper_disable(enum umh_disable_depth depth);
 extern void __usermodehelper_set_disable_depth(enum umh_disable_depth depth);
 
diff --git a/init/main.c b/init/main.c
index c5d5626..45551f8 100644
--- a/init/main.c
+++ b/init/main.c
@@ -877,7 +877,6 @@ static void __init do_initcalls(void)
 static void __init do_basic_setup(void)
 {
 	cpuset_init_smp();
-	usermodehelper_init();
 	shmem_init();
 	driver_init();
 	init_irq_proc();
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 4682e91..d8cc116ab 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -45,8 +45,6 @@
 
 extern int max_threads;
 
-static struct workqueue_struct *khelper_wq;
-
 #define CAP_BSET	(void *)1
 #define CAP_PI		(void *)2
 
@@ -548,7 +546,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 		return -EINVAL;
 	}
 	helper_lock();
-	if (!khelper_wq || usermodehelper_disabled) {
+	if (usermodehelper_disabled) {
 		retval = -EBUSY;
 		goto out;
 	}
@@ -560,7 +558,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 	sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
 	sub_info->wait = wait;
 
-	queue_work(khelper_wq, &sub_info->work);
+	queue_work(system_unbound_wq, &sub_info->work);
 	if (wait == UMH_NO_WAIT)	/* task has freed sub_info */
 		goto unlock;
 
@@ -690,9 +688,3 @@ struct ctl_table usermodehelper_table[] = {
 	},
 	{ }
 };
-
-void __init usermodehelper_init(void)
-{
-	khelper_wq = create_singlethread_workqueue("khelper");
-	BUG_ON(!khelper_wq);
-}
-- 
2.1.4

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