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From: David Miller <davem@davemloft.net>
To: dan.j.williams@intel.com
Cc: linux-kernel@vger.kernel.org, neilb@suse.de,
	galak@kernel.crashing.org, christopher.leech@intel.com,
	alan@lxorguk.ukuu.org.uk
Subject: Re: [PATCH rev2 1/4] dmaengine: enable mutliple clients and operations
Date: Mon, 31 Jul 2006 23:11:58 -0700 (PDT)	[thread overview]
Message-ID: <20060731.231158.91311705.davem@davemloft.net> (raw)
In-Reply-To: <20060728181618.5948.27138.stgit@dwillia2-linux.ch.intel.com>


Can I ask that the known bugs in the I/O AT DMA code be fixed
before we start adding new features to it?

Specifically, the lock_cpu_hotplug() call in net_dma_rebalance()
is still there and being invoked with a spinlock held.  The
spinlock is grabbed by the caller, netdev_dma_event() which
grabs the net_dma_event_lock spinlock.

You cannot invoke lock_cpu_hotplug() while holding a spinlock
because lock_cpu_hotplug(), as seen in kernel/cpu.c, takes
a semaphore which can sleep.  Sleeping while holding a spinlock
is not allowed.

This is the second time I have tried to make the Intel developers
aware of this bug.  So please fix this problem.

Thanks a lot.

  parent reply	other threads:[~2006-08-01  6:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-07-28 18:16 Dan Williams
2006-07-28 18:16 ` [PATCH rev2 2/4] dmaengine: reduce backend address permutations Dan Williams
2006-07-28 18:16 ` [PATCH rev2 3/4] dmaengine: expose per channel dma mapping characteristics to clients Dan Williams
2006-07-28 18:16 ` [PATCH rev2 4/4] dmaengine: add memset as an asynchronous dma operation Dan Williams
2006-08-01  6:11 ` David Miller [this message]
2006-08-01  8:10   ` [PATCH rev2 1/4] dmaengine: enable mutliple clients and operations Andrew Morton
2006-08-01 18:03 Leech, Christopher

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