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xen-devel
Re: [Xen-devel] 3.0.4: Soft lockup in netfront in SMP build
Graham, Simon wrote:
> Just run into a (real) soft lockup running 3.0.4 - stack is at the end of
> this, but basically:
>
> . network_open acquires the rx spin lock with spin_lock() and then checks for
> work on the queue and calls (I think) netif_rx_schedule with the lock still
> held which
> can call into the hypervisor.
> . An interrupt is delivered to the bottom half of netfront which ends up
> calling netif_poll
> which blocks attempting to acquire the rx spin lock.
>
> Oops!
>
> I see from the unstable tree that this code was recently modified to use
> spin_lock_bh() instead of spin_lock() as part of a mega-merge of IA64 code -
> clearly we cant merge this changeset into 3.0.4.
>
> I haven't looked too closely at all of the code yet, but I'm wondering if a
> judicious change of spin_lock to spin_lock_bh in netfront would be the best
> approach?
>
I found a few locking problems when I ran netfront with lockdep
enabled. Fixes were committed to xen-unstable in 14844:abea8d171503 and
14851:22460cfaca71. I was wondering if there had been any real cases of
these deadlocking.
J
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