netdev - Re: MSI interrupts and disable

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Date:	Sat, 06 Oct 2007 13:59:13 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Ayaz Abdulla <aabdulla@...dia.com>,
	Manfred Spraul <manfred@...orfullife.com>,
	nedev <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: MSI interrupts and disable_irq

Yinghai Lu wrote:
> On 9/28/07, Jeff Garzik <jgarzik@...ox.com> wrote:
>> Ayaz Abdulla wrote:
>>> I am trying to track down a forcedeth driver issue described by bug 9047
>>> in bugzilla (2.6.23-rc7-git1 forcedeth w/ MCP55 oops under heavy load).
>>> I added a patch to synchronize the timer handlers so that one handler
>>> doesn't accidently enable the IRQ while another timer handler is running
>>> (see attachment 'Add timer lock' in bug report) and for other processing
>>> protection.
>>>
>>> However, the system still had an Oops. So I added a lock around the
>>> nv_rx_process_optimized() and the Oops has not happened (see attachment
>>> 'New patch for locking' in bug report). This would imply a
>>> synchronization issue. However, the only callers of that function are
>>> the IRQ handler and the timer handlers (in non-NAPI case). The timer
>>> handlers  use disable_irq so that the IRQ handler does not contend with
>>> them. It looks as if disable_irq is not working properly.
>>>
>>> This issue repros only with MSI interrupt and not legacy INTx
>>> interrupts. Any ideas?
>> (added linux-kernel to CC, since I think it's more of a general kernel
>> issue)
>>
> I wonder if the race is between soft_timer for nv_do_nic_poll from
> different CPUs

Interested parties should try the forcedeth patches I just posted :)

	Jeff



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