From: Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH RHEL 5.1] workaround for qla2xxx vs xen swiotlb
Date: Tue, 14 Aug 2007 11:36:34 -0400
Bugzilla: 219216
Message-Id: <46C1CC02.4040404@redhat.com>
Changelog: [misc] workaround for qla2xxx vs xen swiotlb

There is a theoretical problem when the qla2xxx driver fills up
the swiotlb space and shares the system with a driver that will
make the system panic if it cannot get space in the swiotlb.
In that case, the other printks will trigger and we still know
what went wrong.

Here's a version using printk_ratelimit().

Directly using __printk_ratelimit() with a higher timeout
is probably not a good idea, since lower timeout messages
could starve this one completely.

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.

--- linux-2.6.18.noarch/arch/i386/kernel/swiotlb.c.flood	2007-08-13 14:59:05.000000000 -0400
+++ linux-2.6.18.noarch/arch/i386/kernel/swiotlb.c	2007-08-14 11:32:25.000000000 -0400
@@ -403,8 +403,9 @@ swiotlb_full(struct device *dev, size_t 
 	 * When the mapping is small enough return a static buffer to limit
 	 * the damage, or panic when the transfer is too big.
 	 */
-	printk(KERN_ERR "PCI-DMA: Out of SW-IOMMU space for %lu bytes at "
-	       "device %s\n", (unsigned long)size, dev ? dev->bus_id : "?");
+	if (printk_ratelimit())
+		printk(KERN_ERR "PCI-DMA: Out of SW-IOMMU space for %lu bytes at "
+		       "device %s\n", (unsigned long)size, dev ? dev->bus_id : "?");
 
 	if (size > io_tlb_overflow && do_panic) {
 		if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)