Re: Linux 2.6.28-rc8

Ingo Molnar
2008-12-11T20:36:53Z

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, 11 Dec 2008, Ingo Molnar wrote:
> >
> > hm, the warning caught a couple of real bugs already. (one in some
> > cpq driver, another was in some networking driver iirc)
>
> Well, one thing that does irritate me is that it scares people who
> can't do anything about it, and probably _shouldn't_ do anything about
> it.

yeah - and false positives also tend to create apathy and resistence
against kernel warnings - thus drawing tester resources away from more
important bugs.

> I wonder if we should just change the "Warning" message to
> "Informational" or something. Yes, they are often real bugs. But no,
> they're not _automatically_ bugs. Almost all the time when a warning
> triggers, it's really just a developer who wants to know about it, it's
> not something that a user should really care/worry about.

ok. In this case i'd suggest we should just remove the warning. People do
get scared by needless kernel stack dumps - no matter whether it's marked
informational or not.

So how about the patch below, queued up in tip/x86/debug? Arjan, what do
you think?

Ingo

--------------->
>From 2dcae81e819fa5cc0e9310ef8b0c079940df3bf3 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 11 Dec 2008 21:29:51 +0100
Subject: [PATCH] IO resources, x86: remove multi-BAR mapping sanity check

Impact: remove a debug warning

The ioremap() time multi-BAR map warning has been causing false positives:

http://lkml.org/lkml/2008/12/10/432
http://lkml.org/lkml/2008/12/11/136

So remove it for now.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/mm/ioremap.c | 6 ------
include/linux/ioport.h | 1 -
kernel/resource.c | 38 --------------------------------------
3 files changed, 0 insertions(+), 45 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index d4c4307..421b92d 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -220,12 +220,6 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
return (__force void __iomem *)phys_to_virt(phys_addr);

/*
- * Check if the request spans more than any BAR in the iomem resource
- * tree.
- */
- WARN_ON(iomem_map_sanity_check(phys_addr, size));
-
- /*
* Don't allow anybody to remap normal RAM that we're using..
*/
for (pfn = phys_addr >> PAGE_SHIFT;
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 041e95a..0dde772 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -174,7 +174,6 @@ extern struct resource * __devm_request_region(struct device *dev,

extern void __devm_release_region(struct device *dev, struct resource *parent,
resource_size_t start, resource_size_t n);
-extern int iomem_map_sanity_check(resource_size_t addr, unsigned long size);

#endif /* __ASSEMBLY__ */
#endif /* _LINUX_IOPORT_H */
diff --git a/kernel/resource.c b/kernel/resource.c
index 4337063..4b0bc70 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -829,41 +829,3 @@ static int __init reserve_setup(char *str)
}

__setup("reserve=", reserve_setup);
-
-/*
- * Check if the requested addr and size spans more than any slot in the
- * iomem resource tree.
- */
-int iomem_map_sanity_check(resource_size_t addr, unsigned long size)
-{
- struct resource *p = &iomem_resource;
- int err = 0;
- loff_t l;
-
- read_lock(&resource_lock);
- for (p = p->child; p ; p = r_next(NULL, p, &l)) {
- /*
- * We can probably skip the resources without
- * IORESOURCE_IO attribute?
- */
- if (p->start >= addr + size)
- continue;
- if (p->end < addr)
- continue;
- if (PFN_DOWN(p->start) <= PFN_DOWN(addr) &&
- PFN_DOWN(p->end) >= PFN_DOWN(addr + size - 1))
- continue;
- printk(KERN_WARNING "resource map sanity check conflict: "
- "0x%llx 0x%llx 0x%llx 0x%llx %s\n",
- (unsigned long long)addr,
- (unsigned long long)(addr + size - 1),
- (unsigned long long)p->start,
- (unsigned long long)p->end,
- p->name);
- err = -1;
- break;
- }
- read_unlock(&resource_lock);
-
- return err;
-}