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Date: Wed, 18 Jan 2017 15:12:55 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "byungchul.park" <byungchul.park@lge.com>
Cc: "'Boqun Feng'" <boqun.feng@gmail.com>, mingo@kernel.org,
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Subject: Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation
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On Wed, Jan 18, 2017 at 09:14:59PM +0900, byungchul.park wrote:

> +Example 3:
> +
> +   CONTEXT X		   CONTEXT Y
> +   ---------		   ---------
> +			   mutex_lock A
> +   mutex_lock A
> +   mutex_unlock A
> +			   wait_for_complete B /* DEADLOCK */

Each line (across both columns) is a distinct point in time after the
line before.

Therefore, this states that "mutex_unlock A" happens before
"wait_for_completion B", which is clearly impossible.

You don't have to remove everything after mutex_lock A, but the unlock
must not happen before context Y does the unlock.