4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yisheng Xie <xieyishe...@huawei.com>


[ 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.

Link: 
http://lkml.kernel.org/r/1511439788-20099-1-git-send-email-xieyishe...@huawei.com
Signed-off-by: Yisheng Xie <xieyishe...@huawei.com>
Suggested-by: Catalin Marinas <catalin.mari...@arm.com>
Acked-by: Catalin Marinas <catalin.mari...@arm.com>
Cc: Michal Hocko <mho...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 mm/kmemleak.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1532,6 +1532,8 @@ 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();


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