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Date: Tue, 01 Oct 2013 22:46:32 -0400
From: Mark Lord <kernel@start.ca>
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To: Alexander Gordeev <agordeev@redhat.com>
Subject: Re: [PATCH v2 2/6] PCI/MSI: Factor out pci_get_msi_cap() interface
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Cc: linuxppc-dev@lists.ozlabs.org, Joerg Roedel <joro@8bytes.org>,
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On 13-09-26 09:03 AM, Alexander Gordeev wrote:
> On Thu, Sep 26, 2013 at 08:32:53AM -0400, Mark Lord wrote:
>> On 13-09-18 05:48 AM, Alexander Gordeev wrote:
>>> The last pattern makes most of sense to me and could be updated with a more
>>> clear sequence - a call to (bit modified) pci_msix_table_size() followed
>>> by a call to pci_enable_msix(). I think this pattern can effectively
>>> supersede the currently recommended "loop" practice.
>>
>> The loop is still necessary, because there's a race between those two calls,
>> so that pci_enable_msix() can still fail due to lack of MSIX slots.
> 
> Moreover, the existing loop pattern is racy and could fail just as easily ;)

Yes, but it then loops again to correct things.

> But (1) that is something drivers should expect and (2) there is basically
> nothing to race against - that is probably the reason it has not been a
> problem for pSeries. So I think we should not care about this.

I always care about race conditions.