Commit 7b1058bc authored Jul 16, 2016 by Bhaktipriya Shridhar Committed by Martin Schwidefsky Jul 18, 2016

s390/cio/chp : Remove deprecated create_singlethread_workqueue



The workqueue "chp_wq" is involved in performing pending
configure tasks for channel paths.

It has a single work item(&cfg_work) and hence doesn't require
ordering. Also, it is not being used on a memory reclaim path.
Hence, the singlethreaded workqueue has been replaced with the use of
system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 687cb7f2

drivers/s390/cio/chp.c

+2 −9

Original line number	Diff line number	Diff line
		@@ -47,8 +47,6 @@ static DEFINE_MUTEX(info_lock);
		/* Time after which channel-path status may be outdated. */
		static unsigned long chp_info_expires;

		/* Workqueue to perform pending configure tasks. */
		static struct workqueue_struct *chp_wq;
		static struct work_struct cfg_work;

		/* Wait queue for configure completion events. */
		@@ -717,7 +715,7 @@ static void cfg_func(struct work_struct *work)
		wake_up_interruptible(&cfg_wait_queue);
		return;
		}
		queue_work(chp_wq, &cfg_work);
		schedule_work(&cfg_work);
		}

		/**
		@@ -735,7 +733,7 @@ void chp_cfg_schedule(struct chp_id chpid, int configure)
		cfg_set_task(chpid, configure ? cfg_configure : cfg_deconfigure);
		cfg_busy = 1;
		mutex_unlock(&cfg_lock);
		queue_work(chp_wq, &cfg_work);
		schedule_work(&cfg_work);
		}

		/**
		@@ -769,11 +767,6 @@ static int __init chp_init(void)
		ret = crw_register_handler(CRW_RSC_CPATH, chp_process_crw);
		if (ret)
		return ret;
		chp_wq = create_singlethread_workqueue("cio_chp");
		if (!chp_wq) {
		crw_unregister_handler(CRW_RSC_CPATH);
		return -ENOMEM;
		}
		INIT_WORK(&cfg_work, cfg_func);
		init_waitqueue_head(&cfg_wait_queue);
		if (info_update())

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