linux-kernel - RE: sata_mv port lockup on hotplug (kernel 2.6.38.2)

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Message-ID: <C1438B59050E1B4C9482FF3266AD6BA32C772DA491@gretna.indigovision.com>
Date:	Thu, 14 Apr 2011 17:50:53 +0100
From:	Bruce Stenning <b.stenning@...igovision.com>
To:	Mark Lord <kernel@...savvy.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>
Subject: RE: sata_mv port lockup on hotplug (kernel 2.6.38.2)

> > One thing I noticed was that there is no spinlock around the
> > mv_save_cached_regs/mv_edma_cfg in mv_hardreset (unlike mv_port_start
> > and mv_port_stop); why is this?
>
> Yeah, I'm suspecting there's a loophole in the logic there somewhere.
>
> I dusted off the 6041 reference card I have here, and played with the cables
> for a while.  Managed to get one port to stop responding to hot plug fairly
> quickly, though I'm not sure how/why.
>
> Then I added a debug printk() to mv_write_main_irq_mask(), with no other
> changes, and that appears to have been enough to change the race timing
> so that I could no longer produce the problem.
>
> Bruce, here's a slightly-ugly patch that should remove all doubt about races
> in the irq_mask.  Please apply it, test with it, and let me know here if the
> issue goes away.
>
> Thanks
>
> [patch]


Hi Mark,

I have tried the patch out and I was able to reproduce the port lockup with it.

I also tried out my tracing in writelfl (without any other changes) and I was
able to lock up a port without any apparent unusual changes to the register
containing the irq masks.  Are there other routes to disabling the irqs?

I shall continue looking.

Cheers,

Bruce.


Bruce Stenning,
IndigoVision,
b <dot> stenning <at> indigovision <dot> com


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