Patch "kmemleak: add scheduling point to kmemleak_scan()" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

kmemleak: add scheduling point to kmemleak_scan()

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kmemleak-add-scheduling-point-to-kmemleak_scan.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Yisheng Xie <[email protected]>
Date: Wed, 29 Nov 2017 16:11:08 -0800
Subject: kmemleak: add scheduling point to kmemleak_scan()

From: Yisheng Xie <[email protected]>

[ Upstream commit bde5f6bc68db51128f875a756e9082a6c6ff7b4c ]

kmemleak_scan() will scan struct page for each node and it can be really large and resulting in a soft lockup. We have seen a soft lockup when do scan while compile kernel:

  watchdog: BUG: soft lockup - CPU#53 stuck for 22s! [bash:10287]
 [...]
  Call Trace:
   kmemleak_scan+0x21a/0x4c0
   kmemleak_write+0x312/0x350
   full_proxy_write+0x5a/0xa0
   __vfs_write+0x33/0x150
   vfs_write+0xad/0x1a0
   SyS_write+0x52/0xc0
   do_syscall_64+0x61/0x1a0
   entry_SYSCALL64_slow_path+0x25/0x25

Fix this by adding cond_resched every MAX_SCAN_SIZE.

---
 mm/kmemleak.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -1442,6 +1442,8 @@ static void kmemleak_scan(void)
 			if (page_count(page) == 0)
 				continue;
 			scan_block(page, page + 1, NULL);
+			if (!(pfn % (MAX_SCAN_SIZE / sizeof(*page))))
+				cond_resched();
 		}
 	}
 	put_online_mems();

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kmemleak-add-scheduling-point-to-kmemleak_scan.patch