linux-kernel - Re: [PATCH v3] mm: memory-failure: use rcu lock instead of tasklist_lock when collect

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Message-ID: <60f989f0-cfe2-61b5-5f5c-afe9584d8755@huawei.com>
Date:   Tue, 5 Sep 2023 14:57:32 +0800
From:   Tong Tiangen <tongtiangen@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Matthew Wilcox <willy@...radead.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Wangkefeng (OS Kernel Lab)" <wangkefeng.wang@...wei.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linmiaohe <linmiaohe@...wei.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm: memory-failure: use rcu lock instead of
 tasklist_lock when collect_procs()



在 2023/9/4 7:41, Andrew Morton 写道:
> On Mon, 28 Aug 2023 10:25:27 +0800 Tong Tiangen <tongtiangen@...wei.com> wrote:
> 
>> We found a softlock issue in our test, analyzed the logs, and found that
>> the relevant CPU call trace as follows:
>>
>> ...
>>
>> By removing the use of tasklist_lock in task list iteration, we can break
>> the softlock chain above.
>>
> 
> So I assume we'd like to backport this fix into -stable kernels?
> 
> If so, are we able to identify a suitble Fixes: target?
> .

After checking the git logs of these functions, the lock-related code
line is available when the functions are first introduced, as follows:

	copy_process(): kernel/fork.c
		commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (tag: v2.6.12-rc2)
		Author: Linus Torvalds <torvalds@...970.osdl.org>
		Date:   Sat Apr 16 15:20:36 2005 -0700
		
			Linux-2.6.12-rc2
		
	wp_page_copy(): mm/memory.c
		commit 2f38ab2c3c7fef04dca0313fd89d91f142ca9281
		Author: Shachar Raindel <raindel@...lanox.com>
		Date:   Tue Apr 14 15:46:32 2015 -0700
		
			mm: refactor do_wp_page, extract the page copy flow
		
	pte_offset_map_lock: include/linux/mm.hq	
		commit c74df32c724a1652ad8399b4891bb02c9d43743a
		Author: Hugh Dickins <hugh@...itas.com>
		Date:   Sat Oct 29 18:16:23 2005 -0700
		
			[PATCH] mm: ptd_alloc take ptlock
	
	collect_procs_anon(): mm/memory-failure.c
		commit 6a46079cf57a7f7758e8b926980a4f852f89b34d
		Author: Andi Kleen <andi@...stfloor.org>
		Date:   Wed Sep 16 11:50:15 2009 +0200
			HWPOISON: The high level memory error handler in the VM v7

Is it appropriate to use the commit of the last introduction 
function(wp_page_copy())?
	Fixes: 2f38ab2c3c7f ("refactor do_wp_page, extract the page copy flow")

Or use the commit introduced by the error reporting 
function(collect_procs_anon())?
	Fixes: 6a46079cf57a ("HWPOISON: The high level memory error handler in 
the VM v7")