From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@kernel.org>, Qian Cai <cai@lca.pw>
Cc: akpm@linux-foundation.org, sergey.senozhatsky.work@gmail.com,
pmladek@suse.com, rostedt@goodmis.org, peterz@infradead.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next v4] mm/hotplug: silence a lockdep splat with printk()
Date: Fri, 17 Jan 2020 15:43:58 +0100 [thread overview]
Message-ID: <0e9b9357-1982-edd3-dbfe-5350c8d6d0eb@redhat.com> (raw)
In-Reply-To: <20200117144209.GA19428@dhcp22.suse.cz>
On 17.01.20 15:42, Michal Hocko wrote:
> On Fri 17-01-20 07:40:15, Qian Cai wrote:
>>
>>
>>> On Jan 17, 2020, at 3:51 AM, David Hildenbrand <david@redhat.com> wrote:
>>>
>>> -> you are accessing the pageblock without the zone lock. It could
>>> change to "isolate" again in the meantime if I am not wrong!
>>
>> Since we are just dumping the state for debugging, it should be fine
>> to accept a bit inaccuracy here due to racing. I could put a bit
>> comments over there.
>
> Sorry, I could have been more specific. The race I was talking about is
> not about accuracy. The current code is racy in that sense already
> because you are looking at a struct page you do not own so its state can
> change at any time. Please note that the zone->lock doesn't really
The pageblock state cannot change with the zone->lock. That's what I was
referring to here. (this specific check)
> prevent from the state transition because that applies only to free
> pages and those are obviously OK. So this is not really different.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-01-17 14:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 2:21 [PATCH -next v4] mm/hotplug: silence a lockdep splat with printk() Qian Cai
2020-01-17 2:49 ` Sergey Senozhatsky
2020-01-17 8:51 ` David Hildenbrand
2020-01-17 8:59 ` Michal Hocko
2020-01-17 9:25 ` David Hildenbrand
2020-01-17 9:40 ` Michal Hocko
2020-01-17 9:42 ` David Hildenbrand
2020-01-17 10:17 ` Michal Hocko
2020-01-17 10:18 ` David Hildenbrand
2020-01-17 12:40 ` Qian Cai
2020-01-17 12:53 ` David Hildenbrand
2020-01-17 13:30 ` Qian Cai
2020-01-17 13:42 ` David Hildenbrand
2020-01-17 14:42 ` Michal Hocko
2020-01-17 14:43 ` David Hildenbrand [this message]
2020-01-17 15:26 ` Michal Hocko
2020-01-17 8:59 ` Michal Hocko
2020-01-17 12:32 ` Qian Cai
2020-01-17 14:39 ` Michal Hocko
2020-01-17 15:05 ` Qian Cai
2020-01-17 15:46 ` Michal Hocko
2020-01-17 18:49 ` Qian Cai
2020-01-17 19:15 ` David Hildenbrand
2020-01-17 19:42 ` Qian Cai
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