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  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 11 May 2022 10:16:37 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     tytso@....edu
Cc:     torvalds@...ux-foundation.org, damien.lemoal@...nsource.wdc.com,
        linux-ide@...r.kernel.org, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        will@...nel.org, tglx@...utronix.de, rostedt@...dmis.org,
        joel@...lfernandes.org, sashal@...nel.org, daniel.vetter@...ll.ch,
        chris@...is-wilson.co.uk, duyuyang@...il.com,
        johannes.berg@...el.com, tj@...nel.org, willy@...radead.org,
        david@...morbit.com, amir73il@...il.com,
        gregkh@...uxfoundation.org, kernel-team@....com,
        linux-mm@...ck.org, akpm@...ux-foundation.org, mhocko@...nel.org,
        minchan@...nel.org, hannes@...xchg.org, vdavydov.dev@...il.com,
        sj@...nel.org, jglisse@...hat.com, dennis@...nel.org, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, vbabka@...e.cz,
        ngupta@...are.org, linux-block@...r.kernel.org,
        paolo.valente@...aro.org, josef@...icpanda.com,
        linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk,
        jack@...e.cz, jack@...e.com, jlayton@...nel.org,
        dan.j.williams@...el.com, hch@...radead.org, djwong@...nel.org,
        dri-devel@...ts.freedesktop.org, rodrigosiqueiramelo@...il.com,
        melissa.srw@...il.com, hamohammed.sa@...il.com, 42.hyeyoo@...il.com
Subject: Re: [PATCH RFC v6 00/21] DEPT(Dependency Tracker)

On Tue, May 10, 2022 at 02:37:40PM +0900, Byungchul Park wrote:
> Ted wrote:
> > On Tue, May 10, 2022 at 09:32:13AM +0900, Byungchul Park wrote:
> > > DEPT is tracking way more objects than Lockdep so it's inevitable to be
> > > slower, but let me try to make it have the similar performance to
> > > Lockdep.
> > 
> > In order to eliminate some of these false positives, I suspect it's
> > going to increase the number of object classes that DEPT will need to
> > track even *more*.  At which point, the cost/benefit of DEPT may get
> > called into question, especially if all of the false positives can't
> > be suppressed.
> 
> Look. Let's talk in general terms. There's no way to get rid of the
> false positives all the way. It's a decision issue for *balancing*
> between considering potential cases and only real ones. Definitely,
> potential is not real. The more potential things we consider, the higher
> the chances are, that false positives appear.
> 
> But yes. The advantage we'd take by detecting potential ones should be
> higher than the risk of being bothered by false ones. Do you think a
> tool is useless if it produces a few false positives? Of course, it'd
> be a problem if it's too many, but otherwise, I think it'd be a great
> tool if the advantage > the risk.
> 
> Don't get me wrong here. It doesn't mean DEPT is perfect for now. The
> performance should be improved and false alarms that appear should be
> removed, of course. I'm talking about the direction.
> 
> For now, there's no tool to track wait/event itself in Linux kernel -
> a subset of the functionality exists tho. DEPT is the 1st try for that
> purpose and can be a useful tool by the right direction.
> 
> I know what you are concerning about. I bet it's false positives that
> are going to bother you once merged. I'll insist that DEPT shouldn't be
> used as a mandatory testing tool until considered stable enough. But
> what about ones who would take the advantage use DEPT. Why don't you
> think of folks who will take the advantage from the hints about
> dependency of synchronization esp. when their subsystem requires very
> complicated synchronization? Should a tool be useful only in a final
> testing stage? What about the usefulness during development stage?
> 
> It's worth noting DEPT works with any wait/event so any lockups e.g.
> even by HW-SW interface, retry logic or the like can be detected by DEPT
> once all waits and events are tagged properly. I believe the advantage
> by that is much higher than the bad side facing false alarms. It's just
> my opinion. I'm goning to respect the majority opinion.

s/take advantage/have the benefit/g

	Byungchul

Powered by blists - more mailing lists