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From: Christoph Hellwig <hch@lst.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	rakesh@tuxera.com, linux-pci@vger.kernel.org,
	linux-nvme@lists.infradead.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] PCI: ensure the PCI device is locked over ->reset_notify calls
Date: Wed, 7 Jun 2017 20:29:36 +0200	[thread overview]
Message-ID: <20170607182936.GA31815@lst.de> (raw)
In-Reply-To: <20170606211443.GB12672@bhelgaas-glaptop.roam.corp.google.com>

On Tue, Jun 06, 2017 at 04:14:43PM -0500, Bjorn Helgaas wrote:
> So I guess the method here is
> dev->driver->err_handler->reset_notify(), and the PCI core should be
> holding device_lock() while calling it?  That makes sense to me;
> thanks a lot for articulating that!

Yes.

> 1) The current patch protects the err_handler->reset_notify() uses by
> adding or expanding device_lock regions in the paths that lead to
> pci_reset_notify().  Could we simplify it by doing the locking
> directly in pci_reset_notify()?  Then it would be easy to verify the
> locking, and we would be less likely to add new callers without the
> proper locking.

We could do that, except that I'd rather hold the lock over a longer
period if we have many calls following each other.  I also have
a patch to actually kill pci_reset_notify() later in the series as
well, as the calling convention for it and ->reset_notify() are
awkward - depending on prepare parameter they do two entirely
different things.  That being said I could also add new
pci_reset_prepare() and pci_reset_done() helpers.

> 2) Stating the rule explicitly helps look for other problems, and I
> think we have a similar problem in all the pcie_portdrv_err_handler
> methods.

Yes, I mentioned this earlier, and I also vaguely remember we got
bug reports from IBM on power for this a while ago.  I just don't
feel confident enough to touch all these without a good test plan.

WARNING: multiple messages have this Message-ID (diff)
From: hch@lst.de (Christoph Hellwig)
Subject: [PATCH 1/3] PCI: ensure the PCI device is locked over ->reset_notify calls
Date: Wed, 7 Jun 2017 20:29:36 +0200	[thread overview]
Message-ID: <20170607182936.GA31815@lst.de> (raw)
In-Reply-To: <20170606211443.GB12672@bhelgaas-glaptop.roam.corp.google.com>

On Tue, Jun 06, 2017@04:14:43PM -0500, Bjorn Helgaas wrote:
> So I guess the method here is
> dev->driver->err_handler->reset_notify(), and the PCI core should be
> holding device_lock() while calling it?  That makes sense to me;
> thanks a lot for articulating that!

Yes.

> 1) The current patch protects the err_handler->reset_notify() uses by
> adding or expanding device_lock regions in the paths that lead to
> pci_reset_notify().  Could we simplify it by doing the locking
> directly in pci_reset_notify()?  Then it would be easy to verify the
> locking, and we would be less likely to add new callers without the
> proper locking.

We could do that, except that I'd rather hold the lock over a longer
period if we have many calls following each other.  I also have
a patch to actually kill pci_reset_notify() later in the series as
well, as the calling convention for it and ->reset_notify() are
awkward - depending on prepare parameter they do two entirely
different things.  That being said I could also add new
pci_reset_prepare() and pci_reset_done() helpers.

> 2) Stating the rule explicitly helps look for other problems, and I
> think we have a similar problem in all the pcie_portdrv_err_handler
> methods.

Yes, I mentioned this earlier, and I also vaguely remember we got
bug reports from IBM on power for this a while ago.  I just don't
feel confident enough to touch all these without a good test plan.

  reply	other threads:[~2017-06-07 18:29 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-01 11:10 avoid null pointer rereference during FLR V2 Christoph Hellwig
2017-06-01 11:10 ` Christoph Hellwig
2017-06-01 11:10 ` [PATCH 1/3] PCI: ensure the PCI device is locked over ->reset_notify calls Christoph Hellwig
2017-06-01 11:10   ` Christoph Hellwig
2017-06-06  5:31   ` Bjorn Helgaas
2017-06-06  5:31     ` Bjorn Helgaas
2017-06-06  7:28     ` Marta Rybczynska
2017-06-06  7:28       ` Marta Rybczynska
2017-06-06 10:48     ` Christoph Hellwig
2017-06-06 10:48       ` Christoph Hellwig
2017-06-06 21:14       ` Bjorn Helgaas
2017-06-06 21:14         ` Bjorn Helgaas
2017-06-07 18:29         ` Christoph Hellwig [this message]
2017-06-07 18:29           ` Christoph Hellwig
2017-06-12 23:14           ` Bjorn Helgaas
2017-06-12 23:14             ` Bjorn Helgaas
2017-06-13  7:08             ` Christoph Hellwig
2017-06-13  7:08               ` Christoph Hellwig
2017-06-13 14:05               ` Bjorn Helgaas
2017-06-13 14:05                 ` Bjorn Helgaas
2017-06-22 20:41             ` Guilherme G. Piccoli
2017-06-22 20:41               ` Guilherme G. Piccoli
2017-06-01 11:10 ` [PATCH 2/3] PCI: split reset_notify method Christoph Hellwig
2017-06-01 11:10   ` Christoph Hellwig
2017-06-01 11:10 ` [PATCH 3/3] PCI: remove __pci_dev_reset and pci_dev_reset Christoph Hellwig
2017-06-01 11:10   ` Christoph Hellwig
2017-06-15  3:11 ` avoid null pointer rereference during FLR V2 Bjorn Helgaas
2017-06-15  3:11   ` Bjorn Helgaas

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