Re: [PATCH rev2 1/4] dmaengine: enable mutliple clients andoperations

From: David Miller
Date: Tue Aug 01 2006 - 02:10:26 EST

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.
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