Messages in this thread | | | Date | Fri, 3 Sep 2010 13:19:41 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH -resend 1/1] HPET: unmap unused I/O space |
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On Fri, 3 Sep 2010 10:27:54 +0200 Jiri Slaby <jslaby@suse.cz> wrote:
> When the initialization code in hpet founds a memory resource and does > not found IRQ, it does not unmap the memory resource previously > mapped. > > There are buggy BIOSes which report resources exactly like this and > what is worse the memory region bases point to normal RAM. This > normally would not matter since the space is not touched. But when PAT > is turned on, ioremap causes the page to be uncached and sets this bit > in page->flags. > > Then when the page is about to be used by the allocator, it is > reported as: > BUG: Bad page state in process md5sum pfn:3ed00 > page:ffffea0000dbd800 count:0 mapcount:0 mapping:(null) index:0x0 > page flags: 0x20000001000000(uncached) > Pid: 7956, comm: md5sum Not tainted 2.6.34-12-desktop #1 > Call Trace: > [<ffffffff810df851>] bad_page+0xb1/0x100 > [<ffffffff810dfa45>] prep_new_page+0x1a5/0x1c0 > [<ffffffff810dfe01>] get_page_from_freelist+0x3a1/0x640 > [<ffffffff810e01af>] __alloc_pages_nodemask+0x10f/0x6b0
Well damn, good detective work. I wonder how many of those nasty random bad-page-state bug reports just got fixed. I dub thee September's "Hero of the Linux kernel"!
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