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Date: Mon, 7 Apr 2014 10:13:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, devel@openvz.org, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH -mm 2/3] lockdep: mark rwsem_acquire_read as recursive
Message-ID: <20140407081336.GC11096@twins.programming.kicks-ass.net>
References: <cover.1396779337.git.vdavydov@parallels.com>
 <8c6473e959a4557d8622a6d7ff24888cb3f7512d.1396779337.git.vdavydov@parallels.com>
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On Sun, Apr 06, 2014 at 07:33:51PM +0400, Vladimir Davydov wrote:
> rw_semaphore implementation allows recursing calls to down_read, but
> lockdep thinks that it doesn't. As a result, it will complain
> false-positively, e.g. if we do not observe some predefined locking
> order when taking an rw semaphore for reading and a mutex.
> 
> This patch makes lockdep think rw semaphore is read-recursive, just like
> rw spin lock.

Uhm no rwsem isn't read recursive.

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Date: Mon, 7 Apr 2014 10:13:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH -mm 2/3] lockdep: mark rwsem_acquire_read as recursive
Message-ID: <20140407081336.GC11096@twins.programming.kicks-ass.net>
References: <cover.1396779337.git.vdavydov@parallels.com>
 <8c6473e959a4557d8622a6d7ff24888cb3f7512d.1396779337.git.vdavydov@parallels.com>
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To: Vladimir Davydov <vdavydov@parallels.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, devel@openvz.org, Ingo Molnar <mingo@redhat.com>

On Sun, Apr 06, 2014 at 07:33:51PM +0400, Vladimir Davydov wrote:
> rw_semaphore implementation allows recursing calls to down_read, but
> lockdep thinks that it doesn't. As a result, it will complain
> false-positively, e.g. if we do not observe some predefined locking
> order when taking an rw semaphore for reading and a mutex.
> 
> This patch makes lockdep think rw semaphore is read-recursive, just like
> rw spin lock.

Uhm no rwsem isn't read recursive.

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