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From: "Pali Rohár" <pali@kernel.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Bjorn Helgaas" <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Gregory Clement" <gregory.clement@bootlin.com>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Yinghai Lu" <yinghai@kernel.org>
Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files
Date: Wed, 4 Nov 2020 17:46:47 +0100	[thread overview]
Message-ID: <20201104164647.pctgyk2cbhjcq65z@pali> (raw)
In-Reply-To: <20201006222222.GA3221382@bjorn-Precision-5520>

On Tuesday 06 October 2020 17:22:22 Bjorn Helgaas wrote:
> It's not obvious from the code why we need pci_sysfs_init(), but
> Yinghai hinted [1] that we need to create sysfs after assigning
> resources.  I experimented by removing pci_sysfs_init() and skipping
> the ROM BAR sizing.  In that case, we create sysfs files in
> pci_bus_add_device() and later assign space for the ROM BAR, so we
> fail to create the "rom" sysfs file.
> 
> The current solution to that is to delay the sysfs files until
> pci_sysfs_init(), a late_initcall(), which runs after resource
> assignments.  But I think it would be better if we could create the
> sysfs file when we assign the BAR.  Then we could get rid of the
> late_initcall() and that implicit ordering requirement.
> 
> But I haven't tried to code it up, so it's probably more complicated
> than this.  I guess ideally we would assign all the resources before
> pci_bus_add_device().  If we could do that, we could just remove
> pci_sysfs_init() and everything would just work, but I think that's a
> HUGE can of worms.
> 
> [1] https://lore.kernel.org/linux-pci/CAE9FiQWBXHgz-gWCmpWLaBOfQQJwtRZemV6Ut9GVw_KJ-dTGTA@mail.gmail.com/

I found out that pci_sysfs_init() function was introduced in kernel
version 2.6.10 by this historic commit:

https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=f6d553444da20cd1e44f2c4864c2d0c56c934e0a

So it was really due to PCI ROM BAR and accessing it from sysfs.

  parent reply	other threads:[~2020-11-04 16:46 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-16 11:04 PCI: Race condition in pci_create_sysfs_dev_files Pali Rohár
2020-08-14  8:08 ` Pali Rohár
2020-09-09 11:28   ` Pali Rohár
2020-10-05  8:20     ` Pali Rohár
2020-10-05 13:54       ` Bjorn Helgaas
2020-10-06 22:22     ` Bjorn Helgaas
2020-10-07  1:47       ` Oliver O'Halloran
2020-10-07  8:14         ` Pali Rohár
2020-10-07 16:14           ` Bjorn Helgaas
2020-10-08 19:59             ` Bjorn Helgaas
2020-10-09  8:08               ` Pali Rohár
2020-11-04 16:29                 ` Pali Rohár
2020-11-15  6:19                   ` Krzysztof Wilczyński
2020-11-15 12:10                     ` Pali Rohár
2020-10-07  8:12       ` Pali Rohár
2021-04-07 14:25         ` Petr Štetiar
2021-04-07 14:51           ` Pali Rohár
2021-04-07 15:30             ` Petr Štetiar
2021-06-25 11:29               ` Koen Vandeputte
2021-06-25 11:54                 ` Pali Rohár
2021-10-13  6:18                   ` Dexuan-Linux Cui
2021-11-18  3:09                     ` Krzysztof Wilczyński
2021-11-18  3:42                       ` Dexuan Cui
2020-11-04 16:46       ` Pali Rohár [this message]
2021-04-07 14:41 ` Pali Rohár

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