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Date:   Tue, 20 Nov 2018 22:12:21 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Hugh Dickins <hughd@google.com>, Vlastimil Babka <vbabka@suse.cz>,
        pifang@redhat.com, David Hildenbrand <david@redhat.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, aarcange@redhat.com,
        Mel Gorman <mgorman@suse.de>
Subject: Re: Memory hotplug softlock issue
Message-ID: <20181120141221.GA7386@MiWiFi-R3L-srv>
References: <20181119125121.GK22247@dhcp22.suse.cz>
 <20181119141016.GO22247@dhcp22.suse.cz>
 <20181119173312.GV22247@dhcp22.suse.cz>
 <alpine.LSU.2.11.1811191215290.15640@eggly.anvils>
 <20181119205907.GW22247@dhcp22.suse.cz>
 <20181120015644.GA5727@MiWiFi-R3L-srv>
 <alpine.LSU.2.11.1811192127130.2848@eggly.anvils>
 <3f1a82a8-f2aa-ac5e-e6a8-057256162321@suse.cz>
 <20181120135803.GA3369@MiWiFi-R3L-srv>
 <20181120140524.GI22247@dhcp22.suse.cz>
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On 11/20/18 at 03:05pm, Michal Hocko wrote:
> > Yes, I applied Hugh's patch 8 hours ago, then our QE Ping operated on
> > that machine, after many times of hot removing/adding, the endless
> > looping during mirgrating is not seen any more. The test result for
> > Hugh's patch is positive. I even suggested Ping increasing the memory
> > pressure to "stress -m 250", it still succeeded to offline and remove.
> > 
> > So I think this patch works to solve the issue. Thanks a lot for your
> > help, all of you. 
> 
> This is a great news! Thanks for your swift feedback. I will go and try
> to review Hugh's patch soon.

Yeah. Thanks a lot for your help on debugging and narrowing down
to position the cause of the issue, Michal, really appreciated!

> > Meanwhile we found sometime onlining page may not add back all memory
> > blocks on one memory board, then hot removing/adding them will cause
> > kernel panic. I will investigate further and collect information, see if
> > it's a kernel issue or udev issue.
> 
> It would be great to get a report in a new email thread.

Sure, will do after reproducing and inforamtion arranging.

Thanks
Baoquan