linux-kernel - Re: [PATCH 1/3] pci: Rework config space blocking services

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Message-ID: <20111102135951.3bce8b08@jbarnes-desktop>
Date:	Wed, 2 Nov 2011 13:59:51 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Jan Kiszka <jan.kiszka@...mens.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Hans J. Koch" <hjk@...sjkoch.de>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org,
	Brian King <brking@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/3] pci: Rework config space blocking services

On Mon, 12 Sep 2011 18:54:02 +0200
Jan Kiszka <jan.kiszka@...mens.com> wrote:

> pci_block_user_cfg_access was designed for the use case that a single
> context, the IPR driver, temporarily delays user space accesses to the
> config space via sysfs. This assumption became invalid by the time
> pci_dev_reset was added as locking instance. Today, if you run two loops
> in parallel that reset the same device via sysfs, you end up with a
> kernel BUG as pci_block_user_cfg_access detect the broken assumption.
> 
> This reworks the pci_block_user_cfg_access to a sleeping service
> pci_cfg_access_lock and an atomic-compatible variant called
> pci_cfg_access_trylock. The former not only blocks user space access as
> before but also waits if access was already locked. The latter service
> just returns false in this case, allowing the caller to resolve the
> conflict instead of raising a BUG.
> 
> Adaptions of the ipr driver were originally written by Brian King.

Sorry to ask you to refresh these after so long, Jan, but can you
respin against my linux-next branch?

My inbox is a poor substitute for patchwork, but that's no excuse for
leaving you hanging so long.  Sorry!

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center

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