linux-kernel - Re: kernel BUG at fs/dcache.c:648! with v3.11-7890-ge5c832d

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Date:	Tue, 10 Sep 2013 21:12:39 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Waiman Long <waiman.long@...com>,
	Mace Moneta <moneta.mace@...il.com>,
	Josh Boyer <jwboyer@...il.com>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: kernel BUG at fs/dcache.c:648! with v3.11-7890-ge5c832d

On Tue, Sep 10, 2013 at 8:56 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> I do.  What we need on the second pass (one where we currently
> take seq_writelock()) is exclusion against writers; nothing we are
> doing is worth disturbing the readers - we don't change any data
> structures.  And simple grabbing the spinlock, without touching the
> sequence number would achieve exactly that.  Writers will have to
> wait and won't be able to disturb us, readers won't notice anything
> happening.  So yes, this extra primitive does make sense here.

Ahh. Yes, as a fallback from the reader-side sequence lock that makes
perfect sense..

              Linus
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