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

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Date:	Tue, 12 Apr 2011 10:07:35 -0400
From:	Mark Lord <kernel@...savvy.com>
To:	Bruce Stenning <b.stenning@...igovision.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)

On 11-04-12 06:30 AM, Bruce Stenning wrote:
>
> I have reproduced the issue with the 2.6.32 kernel.

Perfect.  This means that it probably wasn't broken by somebody else
since I last looked at the code two years ago.  :)
>
> In case it is of use, the silicon is rev 09 (i.e. C0 stepping) and I am using
> gcc 4.4.2 to build the kernel and modules.

"C0" is *good*.

> I am currently inserting tracing into 2.6.38.2 to try to work out what is going
> on.  From mv_write_main_irq_mask I can see that the IRQ for each port is still
> enabled, even when ports stop responding.  I see interrupts generated when I
> hotplug or unplug disks on ports that are not locked up, but no interrupt is
> generated at all for the ports that are locked (this is from tracing in
> asm_do_IRQ in arch/arm/kernel/irq.c)
> 
> 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?

The mv_hardreset path is run from a libata-eh thread,
and it assumes it has exclusive access to the hardware.

But by all means, stuff the spinlock around that pair of calls,
just to eliminate any possibility of my mis-thinking it there.

I'm going to take a few minutes now and try to re-understand
how hot-plug gets "armed" for use, and see if anything cries out at me.

Cheers
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