thp: freeze khugepaged and ksmd

It's unclear why schedule friendly kernel threads can't be taken away by
the CPU through the scheduler itself.  It's safer to stop them as they can
trigger memory allocation, if kswapd also freezes itself to avoid
generating I/O they have too.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 39d7df40c067..45b6d53bcfbc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -15,6 +15,7 @@
 #include <linux/mm_inline.h>
 #include <linux/kthread.h>
 #include <linux/khugepaged.h>
+#include <linux/freezer.h>
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
 #include "internal.h"
@@ -2085,6 +2086,9 @@ static void khugepaged_do_scan(struct page **hpage)
                         break;
 #endif
 
+                if (unlikely(kthread_should_stop() || freezing(current)))
+                        break;
+
                 spin_lock(&khugepaged_mm_lock);
                 if (!khugepaged_scan.mm_slot)
                         pass_through_head++;
@@ -2147,6 +2151,9 @@ static void khugepaged_loop(void)
                 if (hpage)
                         put_page(hpage);
 #endif
+                try_to_freeze();
+                if (unlikely(kthread_should_stop()))
+                        break;
                 if (khugepaged_has_work()) {
                         DEFINE_WAIT(wait);
                         if (!khugepaged_scan_sleep_millisecs)
@@ -2157,8 +2164,8 @@ static void khugepaged_loop(void)
                                         khugepaged_scan_sleep_millisecs));
                         remove_wait_queue(&khugepaged_wait, &wait);
                 } else if (khugepaged_enabled())
-                        wait_event_interruptible(khugepaged_wait,
-                                                 khugepaged_wait_event());
+                        wait_event_freezable(khugepaged_wait,
+                                             khugepaged_wait_event());
         }
 }
 
@@ -2166,6 +2173,7 @@ static int khugepaged(void *none)
 {
         struct mm_slot *mm_slot;
 
+        set_freezable();
         set_user_nice(current, 19);
 
         /* serialize with start_khugepaged() */
@@ -2180,6 +2188,8 @@ static int khugepaged(void *none)
                 mutex_lock(&khugepaged_mutex);
                 if (!khugepaged_enabled())
                         break;
+                if (unlikely(kthread_should_stop()))
+                        break;
         }
 
         spin_lock(&khugepaged_mm_lock);