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Date: Fri, 17 Jul 2015 15:12:52 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Nicolai Stange <nicstange@gmail.com>,
        Dave Hansen <dave.hansen@intel.com>, Alex Ng <alexng@microsoft.com>,
        Fengguang Wu <fengguang.wu@intel.com>, Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] mm, meminit: replace rwsem with completion
Message-ID: <20150717131252.GL19282@twins.programming.kicks-ass.net>
References: <1437135724-20110-1-git-send-email-mgorman@suse.de>
 <1437135724-20110-2-git-send-email-mgorman@suse.de>
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On Fri, Jul 17, 2015 at 01:22:02PM +0100, Mel Gorman wrote:
> From: Nicolai Stange <nicstange@gmail.com>
> 
> Commit 0e1cc95b4cc7 ("mm: meminit: finish initialisation of struct pages
> before basic setup") introduced a rwsem to signal completion of the
> initialization workers.
> 
> Lockdep complains about possible recursive locking:
>   =============================================
>   [ INFO: possible recursive locking detected ]
>   4.1.0-12802-g1dc51b8 #3 Not tainted
>   ---------------------------------------------
>   swapper/0/1 is trying to acquire lock:
>   (pgdat_init_rwsem){++++.+},
>     at: [<ffffffff8424c7fb>] page_alloc_init_late+0xc7/0xe6
> 
>   but task is already holding lock:
>   (pgdat_init_rwsem){++++.+},
>     at: [<ffffffff8424c772>] page_alloc_init_late+0x3e/0xe6
> 
> Replace the rwsem by a completion together with an atomic
> "outstanding work counter".
> 
> [peterz@infradead.org: Barrier removal on the grounds of being pointless]
> [mgorman@suse.de: Applied review feedback]
> Signed-off-by: Nicolai Stange <nicstange@gmail.com>
> Signed-off-by: Mel Gorman <mgorman@suse.de>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Thanks!