On Fri, 2013-02-15 at 22:23 -0500, [email protected] wrote: > On Thu, Feb 14, 2013 at 05:04:07AM +0000, Ben Hutchings wrote: > > On Tue, 2013-02-12 at 00:01 -0500, [email protected] wrote: > > > Okay, I finally have located the patch causing this bizzare problem > > > for me. Before I discuss it, I'm going to drag out the kernel bug > > > reporting > > > guidelines and try to make a proper bug report out of this. > > > > > > [1.] One line summary of the problem: > > > 3.2.38 most of the time has 100% cpu use reported > > > > > > [2.] Full description of the problem/report: > > > Reverse applying the patch for > > > > > > [9a1f08a1a192f9177d7063d903773aed800b840f] drivers/firmware/dmi_scan.c: > > > fetch dmi version from SMBIOS if it exists > > > > > > on top of a clean 3.2.38 tree makes the problem go away. > > [...] > > > I have to admit I have no idea what the patch I'm reversing actually does, > > > > It changes how we look for the version of a BIOS interface (DMI or > > SMBIOS). All the code that it touches, and the version number variable, > > are discarded after boot and therefore can have very limited effect on > > what happens later! > > Actually upon poking about, I noticed something VERY different about what > the patch does to my computer during the boot process. Let me show you > dmesg output from a good kernel without the patch, then a bad one with the > patch, then I'll point out the important differences I noticed: [...] > Important bits I noticed: The 'bad' kernel initially boots with acpi > disabled, then later turns it back on, whereas the 'good' one boots with > acpi completely enabled with no problems. > > Also, very early on just after yelling about the NX bit not existing in my > cpu, it says this: (-good/+bad) > > -[ 0.000000] DMI 2.3 present. > -[ 0.000000] DMI: ECS M848A/M848A, BIOS 07.00T 04/02/01 > +[ 0.000000] Legacy DMI 0.0 present. > +[ 0.000000] DMI: , BIOS
Oh wow, this has really gone very wrong.
> The 'good' kernel without the patch finds something for DMI (That is in fact
> my motherboard model number, so I know it's doing *something* right) whereas
> the bad one with the patch... Does not.
>
> Anyway, I suppose I could try using acpi=force as the kernel suggests for a
> workaround for now, but I'm still convinced something went wrong with that
> patch now more than ever. Due to the fact that ACPI gets reenabled I didn't
> catch on that something was going wrong so early in the boot process with it
> until now.
>
> One thing I want to emphasize is that the only difference between the two
> kernels is that lone patch.
>
> As for perf top, I tried running it as you suggested, but I honestly can't
> figure out how to get this thing to dump output to a file. Every time I
> redirect stdio/stderr I get a empty file, I don't know what I'm doing wrong.
> Any tips?
[...]
Don't worry about it - I think the log messages are a pretty good clue.
Does this patch fix the log messages and/or the other issues?
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -416,6 +416,9 @@ static int __init dmi_present(const char __iomem *p)
memcpy_fromio(buf, p, 15);
if (dmi_checksum(buf, 15)) {
+ print_hex_dump(KERN_INFO, "DMI entry: ", DUMP_PREFIX_NONE,
+ 16, 1, buf, 15, false);
+
dmi_num = (buf[13] << 8) | buf[12];
dmi_len = (buf[7] << 8) | buf[6];
dmi_base = (buf[11] << 24) | (buf[10] << 16) |
@@ -442,10 +445,12 @@ static int __init dmi_present(const char __iomem *p)
static int __init smbios_present(const char __iomem *p)
{
u8 buf[32];
- int offset = 0;
memcpy_fromio(buf, p, 32);
if ((buf[5] < 32) && dmi_checksum(buf, buf[5])) {
+ print_hex_dump(KERN_INFO, "SMBIOS entry: ", DUMP_PREFIX_NONE,
+ 16, 1, buf, 16, false);
+
dmi_ver = (buf[6] << 8) + buf[7];
/* Some BIOS report weird SMBIOS version, fix that up */
@@ -461,9 +466,9 @@ static int __init smbios_present(const char __iomem *p)
dmi_ver = 0x0206;
break;
}
- offset = 16;
+ return dmi_present(p + 16);
}
- return dmi_present(buf + offset);
+ return 1;
}
void __init dmi_scan_machine(void)
--- END ---
If not, can you report back the 'SMBIOS entry:' and 'DMI entry:' log
lines this produces.
Ben.
--
Ben Hutchings
Computers are not intelligent. They only think they are.
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