From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id 601396B0069 for ; Sat, 17 Sep 2016 22:32:36 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id n185so153276208qke.2 for ; Sat, 17 Sep 2016 19:32:36 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id l123si4257224ywc.88.2016.09.17.19.32.34 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sat, 17 Sep 2016 19:32:35 -0700 (PDT) From: zhongjiang Subject: [PATCH] mm,ksm: fix endless looping in allocating memory when ksm enable Date: Sun, 18 Sep 2016 10:26:10 +0800 Message-ID: <1474165570-44398-1-git-send-email-zhongjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: hughd@google.com, mhocko@suse.cz, akpm@linux-foundation.org, qiuxishi@huawei.com, guohanjun@huawei.com Cc: linux-mm@kvack.org From: zhong jiang I hit the following issue when run a OOM case of the LTP and ksm enable. Call trace: [] __switch_to+0x74/0x8c [] __schedule+0x23c/0x7bc [] schedule+0x3c/0x94 [] rwsem_down_write_failed+0x214/0x350 [] down_write+0x64/0x80 [] __ksm_exit+0x90/0x19c [] mmput+0x118/0x11c [] do_exit+0x2dc/0xa74 [] do_group_exit+0x4c/0xe4 [] get_signal+0x444/0x5e0 [] do_signal+0x1d8/0x450 [] do_notify_resume+0x70/0x78 it will leads to a hung task because the exiting task cannot get the mmap sem for write. but the root cause is that the ksmd holds it for read while allocateing memory which just takes ages to complete. and ksmd will loop in the following path. scan_get_next_rmap_item down_read get_next_rmap_item alloc_rmap_item #ksmd will loop permanently. we fix it by changing the GFP to allow the allocation sometimes fail, and we're not at all interested in hearing abot that. CC: Suggested-by: Hugh Dickins Suggested-by: Michal Hocko Signed-off-by: zhong jiang --- mm/ksm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index 73d43ba..5048083 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -283,7 +283,8 @@ static inline struct rmap_item *alloc_rmap_item(void) { struct rmap_item *rmap_item; - rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); + rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | + __GFP_NORETRY | __GFP_NOWARN); if (rmap_item) ksm_rmap_items++; return rmap_item; -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org