Re: [2/4] 2.6.22-rc3: known regressions

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 31 May 2007 16:17:00 -0700
Roland Dreier <rdreier@cisco.com> wrote:

> What about the changes to fix the order that MSI-X irqs are returned
> in (iirc, list_add had to be changed to list_add_tail in a couple of
> places).  Without that change, multiple MSI-X interrupts seem to be
> broken: the kernel programs the MSI-X table in the opposite order that
> it gives the irq numbers to the driver.  The net effect is that if I
> request, say, 3 MSI-X interrupts for a device, then when the device
> generates the first interrupt, the driver thinks it generated the
> third interrupt, and things go fairly haywire.
> 

That's msi-fix-the-ordering-of-msix-irqs.patch, which is also queued for
the next batch.


"next batch" == around 40 patches atm.  Some of these need maintainer acks
so they will be further delayed, or more likely just merged without the
appropriate ack.



From: "Eric W. Biederman" <ebiederm@xmission.com>

"Mike Miller (OS Dev)" <mikem@beardog.cca.cpqcorp.net> writes:

Found what seems the problem with our vectors being listed backward.  In
drivers/pci/msi.c we should be using list_add_tail rather than list_add to
preserve the ordering across various kernels.  Please consider this for
inclusion.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Screwed-up-by: Michael Ellerman <michael@ellerman.id.au>
Cc: "Mike Miller (OS Dev)" <mikem@beardog.cca.cpqcorp.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/pci/msi.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff -puN drivers/pci/msi.c~msi-fix-the-ordering-of-msix-irqs drivers/pci/msi.c
--- a/drivers/pci/msi.c~msi-fix-the-ordering-of-msix-irqs
+++ a/drivers/pci/msi.c
@@ -333,7 +333,7 @@ static int msi_capability_init(struct pc
 			msi_mask_bits_reg(pos, is_64bit_address(control)),
 			maskbits);
 	}
-	list_add(&entry->list, &dev->msi_list);
+	list_add_tail(&entry->list, &dev->msi_list);
 
 	/* Configure MSI capability structure */
 	ret = arch_setup_msi_irqs(dev, 1, PCI_CAP_ID_MSI);
@@ -404,7 +404,7 @@ static int msix_capability_init(struct p
 		entry->dev = dev;
 		entry->mask_base = base;
 
-		list_add(&entry->list, &dev->msi_list);
+		list_add_tail(&entry->list, &dev->msi_list);
 	}
 
 	ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
_

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