From: Michal Hocko <mhocko@kernel.org>
To: "zhaowuyun@wingtech.com" <zhaowuyun@wingtech.com>
Cc: mgorman <mgorman@techsingularity.net>,
akpm <akpm@linux-foundation.org>, minchan <minchan@kernel.org>,
vinmenon <vinmenon@codeaurora.org>, hannes <hannes@cmpxchg.org>,
"hillf.zj" <hillf.zj@alibaba-inc.com>,
linux-mm <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Hugh Dickins <hughd@google.com>
Subject: Re: Re: [PATCH] [PATCH] mm: disable preemption before swapcache_free
Date: Wed, 25 Jul 2018 12:32:04 +0200 [thread overview]
Message-ID: <20180725103204.GY28386@dhcp22.suse.cz> (raw)
In-Reply-To: <20180725082100.GV28386@dhcp22.suse.cz>
On Wed 25-07-18 10:21:00, Michal Hocko wrote:
> [Please do not top post - thank you]
> [CC Hugh - the original patch was http://lkml.kernel.org/r/2018072514375722198958@wingtech.com]
now for real
> On Wed 25-07-18 15:57:55, zhaowuyun@wingtech.com wrote:
> > That is a BUG we found in mm/vmscan.c at KERNEL VERSION 4.9.82
>
> The code is quite similar in the current tree as well.
>
> > Sumary is TASK A (normal priority) doing __remove_mapping page preempted by TASK B (RT priority) doing __read_swap_cache_async,
> > the TASK A preempted before swapcache_free, left SWAP_HAS_CACHE flag in the swap cache,
> > the TASK B which doing __read_swap_cache_async, will not success at swapcache_prepare(entry) because the swap cache was exist, then it will loop forever because it is a RT thread...
> > the spin lock unlocked before swapcache_free, so disable preemption until swapcache_free executed ...
>
> OK, I see your point now. I have missed the lock is dropped before
> swapcache_free. How can preemption disabling prevent this race to happen
> while the code is preempted by an IRQ?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-07-25 10:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-25 6:37 [PATCH] [PATCH] mm: disable preemption before swapcache_free zhaowuyun
2018-07-25 6:40 ` zhaowuyun
2018-07-25 7:40 ` Michal Hocko
2018-07-25 7:57 ` zhaowuyun
2018-07-25 8:21 ` Michal Hocko
2018-07-25 9:53 ` zhaowuyun
2018-07-25 10:34 ` Michal Hocko
2018-07-25 11:17 ` zhaowuyun
2018-07-25 10:32 ` Michal Hocko [this message]
2018-07-25 21:16 ` Andrew Morton
2018-07-26 2:21 ` zhaowuyun
2018-07-26 6:06 ` Michal Hocko
2018-07-26 7:03 ` zhaowuyun
2018-07-26 7:44 ` Michal Hocko
2018-07-26 22:11 ` Andrew Morton
2018-07-27 6:07 ` zhaowuyun
2018-08-04 23:07 ` Hugh Dickins
2018-08-07 2:15 ` zhaowuyun
2018-08-07 3:23 ` Hugh Dickins
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