Re: [PATCH v3] mm: memory-failure: use rcu lock instead of tasklist_lock when collect_procs()

[Tong Tiangen]

在 2023/9/4 7:41, Andrew Morton 写道:
> On Mon, 28 Aug 2023 10:25:27 +0800 Tong Tiangen <tongtiangen@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
		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@xxxxxxxxxxxx>
		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@xxxxxxxxxxx>
		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@xxxxxxxxxxxxxx>
		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")