From: Grant Grundler <grundler@parisc-linux.org>
To: Brian King <brking@us.ibm.com>
Cc: Andrew Morton <akpm@osdl.org>,
greg@kroah.com, matthew@wil.cx, benh@kernel.crashing.org,
ak@muc.de, paulus@samba.org, linux-kernel@vger.kernel.org,
alan@lxorguk.ukuu.org.uk, linux-pci@atrey.karlin.mff.cuni.cz
Subject: Re: [PATCH 1/2] pci: Block config access during BIST (resend)
Date: Fri, 2 Sep 2005 16:43:14 -0600 [thread overview]
Message-ID: <20050902224314.GB8463@colo.lackof.org> (raw)
In-Reply-To: <4318E6B3.7010901@us.ibm.com>
On Fri, Sep 02, 2005 at 06:56:35PM -0500, Brian King wrote:
> Andrew Morton wrote:
> >Brian King <brking@us.ibm.com> wrote:
> >
> >>+void pci_block_user_cfg_access(struct pci_dev *dev)
> >>+{
> >>+ unsigned long flags;
> >>+
> >>+ pci_save_state(dev);
> >>+ spin_lock_irqsave(&pci_lock, flags);
> >>+ dev->block_ucfg_access = 1;
> >>+ spin_unlock_irqrestore(&pci_lock, flags);
> >
> >
> >Are you sure the locking in here is meaningful? All it will really do is
> >give you a couple of barriers.
>
> Actually, it is meaningful. It synchronizes the blocking of pci config
> accesses with other pci config accesses that may be going on when this
> function is called. Without the locking, the API cannot guarantee that
> no further user initiated PCI config accesses will be initiated after
> this function is called.
I don't have the impression you understood what Andrew wrote.
dev->block_ucfg_access = 1 is essentially an atomic operation.
AFAIK, Use of the pci_lock doesn't solve any race conditions that mb()
wouldn't solve.
If you had:
spin_lock_irqsave(&pci_lock, flags);
pci_save_state(dev);
dev->block_ucfg_access = 1;
spin_unlock_irqrestore(&pci_lock, flags);
Then I could buy your arguement since the flag now implies
we need to atomically save state and set the flag.
grant
next prev parent reply other threads:[~2005-09-02 22:37 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-10 14:49 [PATCH 1/1] pci: Block config access during BIST (resend) brking
2005-01-10 16:10 ` Andi Kleen
2005-01-10 16:25 ` Brian King
2005-01-10 16:29 ` Andi Kleen
2005-01-10 22:57 ` Brian King
2005-01-11 14:37 ` Alan Cox
2005-01-11 17:33 ` Andi Kleen
2005-01-11 22:17 ` Brian King
2005-01-13 15:36 ` Alan Cox
2005-01-13 15:35 ` Alan Cox
2005-01-13 18:03 ` Andi Kleen
2005-01-13 18:46 ` Alan Cox
2005-01-13 20:23 ` Andi Kleen
2005-01-13 19:44 ` Alan Cox
2005-01-13 21:50 ` Andi Kleen
2005-01-15 0:33 ` Alan Cox
2005-01-15 1:44 ` Andi Kleen
2005-01-15 1:01 ` Alan Cox
2005-01-15 6:20 ` Benjamin Herrenschmidt
2005-01-16 0:58 ` Alan Cox
2005-01-16 4:01 ` Benjamin Herrenschmidt
2005-01-16 4:48 ` Andi Kleen
2005-01-16 20:53 ` Benjamin Herrenschmidt
2005-01-16 22:07 ` Andi Kleen
2005-01-16 22:14 ` Benjamin Herrenschmidt
2005-01-16 21:10 ` Alan Cox
2005-01-18 15:14 ` Brian King
2005-01-18 23:31 ` Andi Kleen
2005-01-18 23:36 ` Brian King
2005-01-19 22:40 ` Alan Cox
2005-01-26 16:34 ` Brian King
2005-01-26 22:10 ` Benjamin Herrenschmidt
2005-01-27 15:53 ` Alan Cox
2005-01-27 18:44 ` Brian King
2005-01-27 23:15 ` Benjamin Herrenschmidt
2005-01-28 14:35 ` Brian King
2005-02-01 7:27 ` Greg KH
2005-02-01 15:12 ` Brian King
2005-02-01 15:44 ` Matthew Wilcox
2005-02-01 17:35 ` Brian King
2005-02-01 17:47 ` Matthew Wilcox
2005-02-01 19:01 ` Brian King
2005-02-01 23:00 ` Benjamin Herrenschmidt
2005-02-02 15:33 ` Brian King
2005-02-08 20:08 ` Greg KH
2005-06-21 16:08 ` Brian King
2005-08-23 15:11 ` [PATCH 1/2] " Brian King
2005-08-23 15:14 ` [PATCH 2/2] ipr: " Brian King
2005-09-01 23:03 ` [PATCH 1/2] pci: " Andrew Morton
2005-09-02 23:56 ` Brian King
2005-09-02 22:43 ` Grant Grundler [this message]
2005-09-02 23:11 ` Paul Mackerras
2005-09-03 0:08 ` Grant Grundler
2005-09-03 23:37 ` Brian King
2005-09-03 19:39 ` Grant Grundler
2005-09-05 18:31 ` Brian King
2005-09-06 4:48 ` Grant Grundler
2005-09-06 14:28 ` Brian King
2005-09-07 5:49 ` Paul Mackerras
2005-09-07 14:58 ` Grant Grundler
2005-09-07 22:39 ` Paul Mackerras
2005-09-08 1:21 ` Grant Grundler
2005-09-08 3:05 ` Brian King
2005-09-08 4:08 ` Grant Grundler
2005-02-01 18:58 ` [PATCH 1/1] " Greg KH
2005-02-01 23:07 ` Benjamin Herrenschmidt
2005-02-01 22:58 ` Benjamin Herrenschmidt
2005-01-10 19:23 ` Alan Cox
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