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Date: Wed, 12 Jul 2006 23:14:43 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Roland Dreier <rdreier@cisco.com>
Cc: akpm@osdl.org, Arjan van de Ven <arjan@infradead.org>,
       Zach Brown <zach.brown@oracle.com>, openib-general@openib.org,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Convert idr's internal locking to _irqsave variant
Message-ID: <20060712211443.GA10944@elte.hu>
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* 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.
> 
> Cc: Arjan van de Ven <arjan@infradead.org>
> Cc: Ingo Molnar <mingo@elte.hu>

Acked-by: Ingo Molnar <mingo@elte.hu>

	Ingo