linux-kernel - Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation

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Date:   Wed, 18 Jan 2017 19:53:47 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     peterz@...radead.org, mingo@...nel.org, tglx@...utronix.de,
        walken@...gle.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        npiggin@...il.com
Subject: Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation

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.

No matter which one is chosen, mutex_lock A in CONTEXT X cannot be passed.

> 
> Regards,
> Boqun