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Commit 911891af authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Linus Torvalds
Browse files

thp: move khugepaged_mutex out of khugepaged 



Currently, hugepaged_mutex is used really complexly and hard to
understand, actually, it is just used to serialize start_khugepaged and
khugepaged for these reasons:

- khugepaged_thread is shared between them
- the thp disable path (echo never > transparent_hugepage/enabled) is
  nonblocking, so we need to protect khugepaged_thread to get a stable
  running state

These can be avoided by:

- use the lock to serialize the thread creation and cancel
- thp disable path can not finised until the thread exits

Then khugepaged_thread is fully controlled by start_khugepaged, khugepaged
will be happy without the lock

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 637e3a27

mm/huge_memory.c

+13 −23
Original line number Diff line number Diff line
@@ -139,9 +139,6 @@ static int start_khugepaged(void) 
{

	int err = 0;

	if (khugepaged_enabled()) {

		int wakeup;



		mutex_lock(&khugepaged_mutex);

		if (!khugepaged_thread)

			khugepaged_thread = kthread_run(khugepaged, NULL,

							"khugepaged");
@@ -151,15 +148,17 @@ static int start_khugepaged(void) 
			err = PTR_ERR(khugepaged_thread);

			khugepaged_thread = NULL;

		}

		wakeup = !list_empty(&khugepaged_scan.mm_head);

		mutex_unlock(&khugepaged_mutex);

		if (wakeup)



		if (!list_empty(&khugepaged_scan.mm_head))

			wake_up_interruptible(&khugepaged_wait);



		set_recommended_min_free_kbytes();

	} else

	} else if (khugepaged_thread) {

		/* wakeup to exit */

		wake_up_interruptible(&khugepaged_wait);

		kthread_stop(khugepaged_thread);

		khugepaged_thread = NULL;

	}



	return err;

}
@@ -221,7 +220,12 @@ static ssize_t enabled_store(struct kobject *kobj, 
				TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);



	if (ret > 0) {

		int err = start_khugepaged();

		int err;



		mutex_lock(&khugepaged_mutex);

		err = start_khugepaged();

		mutex_unlock(&khugepaged_mutex);



		if (err)

			ret = err;

	}
@@ -2329,20 +2333,10 @@ static int khugepaged(void *none) 
	set_freezable();

	set_user_nice(current, 19);



	/* serialize with start_khugepaged() */

	mutex_lock(&khugepaged_mutex);



	for (;;) {

		mutex_unlock(&khugepaged_mutex);

	while (!kthread_should_stop()) {

		VM_BUG_ON(khugepaged_thread != current);

		khugepaged_loop();

		VM_BUG_ON(khugepaged_thread != current);



		mutex_lock(&khugepaged_mutex);

		if (!khugepaged_enabled())

			break;

		if (unlikely(kthread_should_stop()))

			break;

	}



	spin_lock(&khugepaged_mm_lock);
@@ -2351,10 +2345,6 @@ static int khugepaged(void *none) 
	if (mm_slot)

		collect_mm_slot(mm_slot);

	spin_unlock(&khugepaged_mm_lock);



	khugepaged_thread = NULL;

	mutex_unlock(&khugepaged_mutex);



	return 0;

}