linux-kernel - Re: [PATCH v5 4/9] pci: Add slot reset option to pci_dev

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Date:	Fri, 16 Aug 2013 07:24:22 +0800
From:	rui wang <ruiv.wang@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Alex Williamson <alex.williamson@...hat.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	Don Dutile <ddutile@...hat.com>,
	Takao Indoh <indou.takao@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 4/9] pci: Add slot reset option to pci_dev_reset

On 8/15/13, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Thu, Aug 8, 2013 at 2:09 PM, Alex Williamson
<snip>
> I don't think this is hotplug-safe.  It looks like pci_bus_sem might
> be the right semaphore to hold while verifying that we won't reset any
> unintended devices.

Something like pci_bus_sem locks all the buses, which may pose a big
overhead. So it doesn't seem like an ideal solution. A better approach
is to lock only one parent to protect only a sub-tree. At least that's
what I've seen in some other operating systems dealing with PCI
hotplug. But that requires a significant amount of change.

Thanks
Rui

  But I think most users of the bus->devices list
> are unprotected, so there's no point in trying to fix just this one.
>
>> +}
>> +
>>  static int __pci_dev_reset(struct pci_dev *dev, int probe)
>>  {
>>         int rc;
>> @@ -3278,6 +3308,10 @@ static int __pci_dev_reset(struct pci_dev *dev, int
>> probe)
>>         if (rc != -ENOTTY)
>>                 goto done;
>>
>> +       rc = pci_dev_reset_slot_function(dev, probe);
>> +       if (rc != -ENOTTY)
>> +               goto done;
>> +
>>         rc = pci_parent_bus_reset(dev, probe);
>>  done:
>>         return rc;
>>
> --
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