From: "byungchul.park" <byungchul.park@lge.com>
To: "'Peter Zijlstra'" <peterz@infradead.org>
Cc: "'Boqun Feng'" <boqun.feng@gmail.com>, <mingo@kernel.org>,
<tglx@linutronix.de>, <walken@google.com>, <kirill@shutemov.name>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<iamjoonsoo.kim@lge.com>, <akpm@linux-foundation.org>,
<npiggin@gmail.com>
Subject: RE: [PATCH v4 15/15] lockdep: Crossrelease feature documentation
Date: Wed, 18 Jan 2017 21:14:59 +0900 [thread overview]
Message-ID: <008101d27184$7d3cbd00$77b63700$@lge.com> (raw)
In-Reply-To: <20170118120757.GD6515@twins.programming.kicks-ass.net>
> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@infradead.org]
> Sent: Wednesday, January 18, 2017 9:08 PM
> To: Byungchul Park
> Cc: Boqun Feng; mingo@kernel.org; tglx@linutronix.de; walken@google.com;
> kirill@shutemov.name; linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> iamjoonsoo.kim@lge.com; akpm@linux-foundation.org; npiggin@gmail.com
> Subject: Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation
>
> On Wed, Jan 18, 2017 at 08:54:28PM +0900, Byungchul Park wrote:
> > On Wed, Jan 18, 2017 at 12:03:17PM +0100, Peter Zijlstra wrote:
> > > On Wed, Jan 18, 2017 at 07:53:47PM +0900, Byungchul Park wrote:
> > > > On Wed, Jan 18, 2017 at 02:42:30PM +0800, Boqun Feng wrote:
> > > > > On Fri, Dec 09, 2016 at 02:12:11PM +0900, Byungchul Park wrote:
> > > > > [...]
> > > > > > +Example 1:
> > > > > > +
> > > > > > + CONTEXT X CONTEXT Y
> > > > > > + --------- ---------
> > > > > > + mutext_lock A
> > > > > > + lock_page B
> > > > > > + lock_page B
> > > > > > + mutext_lock A /* DEADLOCK */
> > > > >
> > > > > s/mutext_lock/mutex_lock
> > > >
> > > > Thank you.
> > > >
> > > > > > +Example 3:
> > > > > > +
> > > > > > + CONTEXT X CONTEXT Y
> > > > > > + --------- ---------
> > > > > > + mutex_lock A
> > > > > > + mutex_lock A
> > > > > > + mutex_unlock A
> > > > > > + wait_for_complete B /* DEADLOCK */
> > > > >
> > > > > I think this part better be:
> > > > >
> > > > > CONTEXT X CONTEXT Y
> > > > > --------- ---------
> > > > > mutex_lock A
> > > > > mutex_lock A
> > > > > wait_for_complete B /* DEADLOCK */
> > > > > mutex_unlock A
> > > > >
> > > > > , right? Because Y triggers DEADLOCK before X could run
> mutex_unlock().
> > > >
> > > > There's no different between two examples.
> > >
> > > There is..
> > >
> > > > No matter which one is chosen, mutex_lock A in CONTEXT X cannot be
> passed.
> > >
> > > But your version shows it does mutex_unlock() before CONTEXT Y does
> > > wait_for_completion().
> > >
> > > The thing about these diagrams is that both columns are assumed to
> have
> > > the same timeline.
> >
> > X cannot acquire mutex A because Y already acquired it.
> >
> > In order words, all statements below mutex_lock A in X cannot run.
>
> But your timeline shows it does, which is the error that Boqun pointed
> out.
I am sorry for not understanding what you are talking about.
Do you mean that I should remove all statements below mutex_lock A in X?
Or should I move mutex_unlock as Boqun said? What will change?
next prev parent reply other threads:[~2017-01-18 12:15 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-09 5:11 [PATCH v4 00/15] lockdep: Implement crossrelease feature Byungchul Park
2016-12-09 5:11 ` [PATCH v4 01/15] x86/dumpstack: Optimize save_stack_trace Byungchul Park
2016-12-09 5:11 ` [PATCH v4 02/15] x86/dumpstack: Add save_stack_trace()_fast() Byungchul Park
2016-12-09 5:11 ` [PATCH v4 03/15] lockdep: Refactor lookup_chain_cache() Byungchul Park
2016-12-09 5:12 ` [PATCH v4 04/15] lockdep: Add a function building a chain between two classes Byungchul Park
2017-01-10 21:00 ` Peter Zijlstra
2017-01-12 1:41 ` Byungchul Park
2016-12-09 5:12 ` [PATCH v4 05/15] lockdep: Make check_prev_add can use a separate stack_trace Byungchul Park
2017-01-12 16:16 ` Peter Zijlstra
2017-01-13 2:45 ` Byungchul Park
2017-01-13 4:09 ` [PATCH] lockdep: Make a stack_trace instance passed to check_prev_add as an arg Byungchul Park
2017-01-13 4:38 ` Byungchul Park
2017-01-13 10:11 ` [PATCH v4 05/15] lockdep: Make check_prev_add can use a separate stack_trace Byungchul Park
2017-01-13 10:17 ` [PATCH 1/2] lockdep: Refactor save_trace() Byungchul Park
2017-01-13 10:17 ` [PATCH 2/2] lockdep: Pass a callback arg to check_prev_add() to handle stack_trace Byungchul Park
2017-01-17 15:54 ` [PATCH v4 05/15] lockdep: Make check_prev_add can use a separate stack_trace Peter Zijlstra
2017-01-18 2:04 ` Byungchul Park
2017-01-18 15:10 ` Peter Zijlstra
2017-01-19 2:47 ` Byungchul Park
2016-12-09 5:12 ` [PATCH v4 06/15] lockdep: Make save_trace can skip stack tracing of the current Byungchul Park
2017-01-12 16:37 ` Peter Zijlstra
2017-01-13 0:18 ` Byungchul Park
2016-12-09 5:12 ` [PATCH v4 07/15] lockdep: Implement crossrelease feature Byungchul Park
2017-01-13 4:39 ` Lai Jiangshan
2017-01-13 5:02 ` Byungchul Park
2017-01-16 15:10 ` Peter Zijlstra
2017-01-17 2:05 ` Byungchul Park
2017-01-17 7:12 ` Peter Zijlstra
2017-01-17 7:49 ` Byungchul Park
2017-01-17 7:14 ` Peter Zijlstra
2017-01-17 7:45 ` Byungchul Park
2017-01-16 15:13 ` Peter Zijlstra
2017-01-17 2:33 ` Byungchul Park
2017-01-17 6:24 ` Boqun Feng
2017-01-17 7:43 ` Byungchul Park
2016-12-09 5:12 ` [PATCH v4 08/15] lockdep: Make crossrelease use save_stack_trace_fast() Byungchul Park
2016-12-09 5:12 ` [PATCH v4 09/15] lockdep: Make print_circular_bug() crosslock-aware Byungchul Park
2016-12-09 5:12 ` [PATCH v4 10/15] lockdep: Apply crossrelease to completion operation Byungchul Park
2016-12-09 5:12 ` [PATCH v4 11/15] pagemap.h: Remove trailing white space Byungchul Park
2016-12-09 5:12 ` [PATCH v4 12/15] lockdep: Apply crossrelease to PG_locked lock Byungchul Park
2016-12-09 5:12 ` [PATCH v4 13/15] lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked Byungchul Park
2016-12-09 5:12 ` [PATCH v4 14/15] lockdep: Move data used in CONFIG_LOCKDEP_PAGELOCK from page to page_ext Byungchul Park
2016-12-09 5:12 ` [PATCH v4 15/15] lockdep: Crossrelease feature documentation Byungchul Park
2017-01-10 20:08 ` Peter Zijlstra
2017-01-11 1:29 ` Byungchul Park
2017-01-18 6:42 ` Boqun Feng
2017-01-18 10:53 ` Byungchul Park
2017-01-18 11:03 ` Peter Zijlstra
2017-01-18 11:54 ` Byungchul Park
2017-01-18 12:07 ` Peter Zijlstra
2017-01-18 12:14 ` byungchul.park [this message]
2017-01-18 14:12 ` Peter Zijlstra
2017-01-19 1:54 ` Byungchul Park
2017-01-18 12:49 ` byungchul.park
2016-12-09 5:21 ` [FYI] Output of 'cat /proc/lockdep' after applying crossrelease Byungchul Park
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