From: Andrew Morton <akpm@osdl.org>
To: Roland Dreier <rdreier@cisco.com>
Cc: arjan@infradead.org, mingo@elte.hu, zach.brown@oracle.com,
openib-general@openib.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Convert idr's internal locking to _irqsave variant
Date: Wed, 12 Jul 2006 18:30:49 -0700 [thread overview]
Message-ID: <20060712183049.bcb6c404.akpm@osdl.org> (raw)
In-Reply-To: <adaveq2v9gn.fsf@cisco.com>
On Wed, 12 Jul 2006 13:45:12 -0700
Roland Dreier <rdreier@cisco.com> wrote:
> Currently, the code in lib/idr.c uses a bare spin_lock(&idp->lock) to
> do internal locking. This is a nasty trap for code that might call
> idr functions from different contexts; for example, it seems perfectly
> reasonable to call idr_get_new() from process context and idr_remove()
> from interrupt context -- but with the current locking this would lead
> to a potential deadlock.
>
> The simplest fix for this is to just convert the idr locking to use
> spin_lock_irqsave().
>
> In particular, this fixes a very complicated locking issue detected by
> lockdep, involving the ib_ipoib driver's priv->lock and dev->_xmit_lock,
> which get involved with the ib_sa module's query_idr.lock.
Sigh. It was always a mistake (of the kernel programming 101 type) to put
any locking at all in the idr code. At some stage we need to weed it all
out and move it to callers.
Your fix is yet more fallout from that mistake.
next prev parent reply other threads:[~2006-07-13 1:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-11 20:10 ipoib lockdep warning Zach Brown
2006-07-11 21:16 ` Michael S. Tsirkin
2006-07-11 21:40 ` Sean Hefty
2006-07-11 21:50 ` [openib-general] " Zach Brown
2006-07-11 22:54 ` Roland Dreier
2006-07-11 23:27 ` Zach Brown
2006-07-11 23:43 ` Roland Dreier
2006-07-11 23:53 ` Zach Brown
2006-07-12 0:06 ` Roland Dreier
2006-07-12 9:38 ` Ingo Molnar
2006-07-12 11:09 ` Michael S. Tsirkin
2006-07-12 16:31 ` [openib-general] " Sean Hefty
2006-07-12 18:56 ` Roland Dreier
2006-07-13 15:55 ` [PATCH] IB/core: use correct gfp_mask in sa_query Michael S. Tsirkin
2006-07-12 19:06 ` [openib-general] ipoib lockdep warning Roland Dreier
2006-07-12 20:45 ` [PATCH] Convert idr's internal locking to _irqsave variant Roland Dreier
2006-07-12 21:14 ` Ingo Molnar
2006-07-13 1:30 ` Andrew Morton [this message]
2006-07-13 15:42 ` Roland Dreier
2006-07-13 20:54 ` Andrew Morton
2006-07-13 21:03 ` Roland Dreier
2006-07-13 21:05 ` Arjan van de Ven
2006-07-14 0:18 ` Roland Dreier
2006-07-14 6:20 ` Arjan van de Ven
2006-07-13 21:43 ` Andrew Morton
2006-07-14 1:08 ` Roland Dreier
2006-07-14 1:18 ` Andrew Morton
2006-07-14 1:30 ` Andrew Morton
2006-07-17 15:57 ` Roland Dreier
2006-07-12 2:33 ` [openib-general] ipoib lockdep warning Roland Dreier
2006-07-12 6:49 ` Arjan van de Ven
2006-07-12 19:01 ` Roland Dreier
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