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: Xiao 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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: Xiao 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Xiao Guangrong · Linus Torvalds
1 parent 637e3a27ec
Showing 1 changed file with 13 additions and 23 deletions Side-by-side Diff
mm/huge_memory.c
@@ -139,9 +139,6 @@
 {
 	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 @@
 			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 @@
 				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 @@
 	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 @@
 	if (mm_slot)
 		collect_mm_slot(mm_slot);
 	spin_unlock(&khugepaged_mm_lock);
-
-	khugepaged_thread = NULL;
-	mutex_unlock(&khugepaged_mutex);
-
 	return 0;
 }
...	...	@@ -139,9 +139,6 @@
139	139	{
140	140	int err = 0;
141	141	if (khugepaged_enabled()) {
142		- int wakeup;
143		-
144		- mutex_lock(&khugepaged_mutex);
145	142	if (!khugepaged_thread)
146	143	khugepaged_thread = kthread_run(khugepaged, NULL,
147	144	"khugepaged");
148	145
149	146
...	...	@@ -151,15 +148,17 @@
151	148	err = PTR_ERR(khugepaged_thread);
152	149	khugepaged_thread = NULL;
153	150	}
154		- wakeup = !list_empty(&khugepaged_scan.mm_head);
155		- mutex_unlock(&khugepaged_mutex);
156		- if (wakeup)
	151	+
	152	+ if (!list_empty(&khugepaged_scan.mm_head))
157	153	wake_up_interruptible(&khugepaged_wait);
158	154
159	155	set_recommended_min_free_kbytes();
160		- } else
	156	+ } else if (khugepaged_thread) {
161	157	/* wakeup to exit */
162	158	wake_up_interruptible(&khugepaged_wait);
	159	+ kthread_stop(khugepaged_thread);
	160	+ khugepaged_thread = NULL;
	161	+ }
163	162
164	163	return err;
165	164	}
...	...	@@ -221,7 +220,12 @@
221	220	TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
222	221
223	222	if (ret > 0) {
224		- int err = start_khugepaged();
	223	+ int err;
	224	+
	225	+ mutex_lock(&khugepaged_mutex);
	226	+ err = start_khugepaged();
	227	+ mutex_unlock(&khugepaged_mutex);
	228	+
225	229	if (err)
226	230	ret = err;
227	231	}
228	232
...	...	@@ -2329,20 +2333,10 @@
2329	2333	set_freezable();
2330	2334	set_user_nice(current, 19);
2331	2335
2332		- /* serialize with start_khugepaged() */
2333		- mutex_lock(&khugepaged_mutex);
2334		-
2335		- for (;;) {
2336		- mutex_unlock(&khugepaged_mutex);
	2336	+ while (!kthread_should_stop()) {
2337	2337	VM_BUG_ON(khugepaged_thread != current);
2338	2338	khugepaged_loop();
2339	2339	VM_BUG_ON(khugepaged_thread != current);
2340		-
2341		- mutex_lock(&khugepaged_mutex);
2342		- if (!khugepaged_enabled())
2343		- break;
2344		- if (unlikely(kthread_should_stop()))
2345		- break;
2346	2340	}
2347	2341
2348	2342	spin_lock(&khugepaged_mm_lock);
...	...	@@ -2351,10 +2345,6 @@
2351	2345	if (mm_slot)
2352	2346	collect_mm_slot(mm_slot);
2353	2347	spin_unlock(&khugepaged_mm_lock);
2354		-
2355		- khugepaged_thread = NULL;
2356		- mutex_unlock(&khugepaged_mutex);
2357		-
2358	2348	return 0;
2359	2349	}
2360	2350