linux-kernel - Re: [RFC] hung_task:add detecting task in D state milliseconds timeout

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAN_w4MVzObz8C3cmK_Ckwsdr1z6m5Q=MGnSsj+vqK_jHXCMr7g@mail.gmail.com>
Date:   Mon, 6 Jul 2020 17:43:06 +0800
From:   yang che <chey84736@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     mcgrof@...nel.org, Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC] hung_task:add detecting task in D state milliseconds timeout

I will learn how to use KernelShark. Try to solve my problem,thanks
for your suggestion.
Talk about I solved a problem with  hung task milliseconds：
   the process get anon_vma read lock when it directly reclaims
memory, but other process down anon_vma write lock,
long time waiting for write lock up. Since anonymous pages can be
inherited from the parent process,
need to analyze whether the anonymous page inherits the parent
process, find is inherits parent process,
use anon_vma's red black tree and  anon_vma_chain find all child
processes have inherited this anonymous page
of the parent process,and analyze the corresponding mapping file of
the current anonymous page in vma.
find what file caused by this problem.
  I used crash+ramdump to analyze this problem before, I will try to
use KernelShark analyze this problem.

I want to ask whether the hung task can be added to support the
detection of millisecond settings？
In theory, there is no harm, and the detection time can be more accurate.

Matthew Wilcox <willy@...radead.org> 于2020年7月6日周一 上午1:18写道：
>
> On Fri, Jul 03, 2020 at 11:18:28AM +0800, yang che wrote:
> >   my understanding, KernelShark can't trigger panic, hung_task can
> > trigger. According to my use,
> > sometimes need to trigger panic to grab ramdump to analyze lock and
> > memory problems.
>
> You shouldn't need to trigger a panic to analyse locking or memory
> problems.  KernelShark is supposed to be able to help you do that without
> bringing down the system.  Give it a try, and if it doesn't work, Steven
> Rostedt is very interested in making it work for your case.