linux-kernel - Re: [Fdutils] DMA cache consistency bug introduced in 2.6.28 (Was: Re: Cannot format floppies under kernel 2.6.*?)

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Date:	Tue, 22 Dec 2009 10:11:48 -0500
From:	Mark Hounschell <markh@...pro.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Mark Hounschell <dmarkh@....rr.com>, Alain Knaff <alain@...ff.lu>,
	linux-kernel@...r.kernel.org, fdutils@...tils.linux.lu
Subject: Re: [Fdutils] DMA cache consistency bug introduced in 2.6.28 (Was:
 Re: Cannot format floppies under kernel 2.6.*?)

On 12/18/2009 03:15 PM, Linus Torvalds wrote:
> 
> 
> On Fri, 18 Dec 2009, Mark Hounschell wrote:
>>
>> It looks like I may have to back up and first find the points that, let me,
>> and stop me,  booting with the HPET enabled. Before I change direction, can
>> the git-bisect start sequence use the SHA1 id for the starting 'goods' and
>> 'bads'? I don't see reference to that in the doc.
> 
> You can always use a SHA1 id instead of a tag. So when you did
> 
> 	git bisect good v2.6.17.4
> 
> you could always have replaced that "v2.6.17.4" with the SHA1 of the 
> commit.
> 
> In git, the SHA1 ID's are the "real" names - the tags and branch names are 
> purely for human-readable decoration. Git always turns them into SHA1 id's 
> internally.
> 
> 		Linus
> 

Ok, I may have something that might help.

# git bisect bad
26afe5f2fbf06ea0765aaa316640c4dd472310c0 is the first bad commit
commit 26afe5f2fbf06ea0765aaa316640c4dd472310c0
Author: venkatesh.pallipadi@...el.com <venkatesh.pallipadi@...el.com>
Date:   Fri Sep 5 18:02:18 2008 -0700

    x86: HPET_MSI Initialise per-cpu HPET timers

    Initialize a per CPU HPET MSI timer when possible. We retain the HPET
    timer 0 (IRQ 0) and timer 1 (IRQ 8) as is when legacy mode is being
used. We
    setup the remaining HPET timers as per CPU MSI based timers. This per CPU
    timer will eliminate the need for timer broadcasting with IRQ 0 when there
    is non-functional LAPIC timer across CPU deep C-states.

    If there are more CPUs than number of available timers, CPUs that do not
    find any timer to use will continue using LAPIC and IRQ 0 broadcast.

    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
    Signed-off-by: Shaohua Li <shaohua.li@...el.com>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>

:040000 040000 b0a11fa0abdc591427e78236a1f25f26b824140e
f2e9b13cf9e2eb7e0fc101660b1e1d499033d78f M      arch


And of coarse this was the first commit that I could not boot if I had hpet
enabled. To get this one to boot (single user mode only) I had to add the
the quiet cmdline option and following patch from to arch/x86/kernel/hpet.c

commit  5ceb1a04187553e08c6ab60d30cee7c454ee139a

@ -445,7 +445,7 @@ static int hpet_setup_irq(struct hpet_dev *dev)
 {

        if (request_irq(dev->irq, hpet_interrupt_handler,
-                       IRQF_SHARED|IRQF_NOBALANCING, dev->name, dev))
+                       IRQF_DISABLED|IRQF_NOBALANCING, dev->name, dev))
                return -1;

        disable_irq(dev->irq);


AND add the quiet cmdline option.

Also, of all the machines it does work on with hpets enabled, I don't see
the HPET2 in /proc/interupts as below.


cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
  0:         82          0          3          0   IO-APIC-edge      timer
  1:          0          0       1712          6   IO-APIC-edge      i8042
  3:          0          0          6          0   IO-APIC-edge
  4:          0          0          6          0   IO-APIC-edge
  6:          0          0          4          0   IO-APIC-edge      floppy
  8:          0          0         60          0   IO-APIC-edge      rtc0
  9:          0          0          0          0   IO-APIC-fasteoi   acpi
 12:          0          0      37798        179   IO-APIC-edge      i8042
 14:          0          0      16462         71   IO-APIC-edge
pata_atiixp
 15:          0          0       5713         17   IO-APIC-edge
pata_atiixp
 16:          0          0        904          2   IO-APIC-fasteoi
aic79xx, ohci_hcd:usb2, ohci_hcd:usb4, HDA Intel, ni-pci-gpib
 17:          0          0          2          0   IO-APIC-fasteoi
ehci_hcd:usb1, parport0, ni-pci-gpib
 18:          0          0      49940         90   IO-APIC-fasteoi
ohci_hcd:usb5, ohci_hcd:usb6, ohci_hcd:usb7, nvidia
 19:          0          0        703          2   IO-APIC-fasteoi
aic7xxx, ehci_hcd:usb3, ttySLG0, eth1
 22:          0          0       1303         15   IO-APIC-fasteoi   ahci


 24:     261763          0          0          0  HPET_MSI-edge      hpet2


 29:          0          0        220          5   PCI-MSI-edge
sky2@pci:0000:04:00.0
NMI:          0          0          0          0   Non-maskable interrupts
LOC:        138     271356     264446     261050   Local timer interrupts
SPU:          0          0          0          0   Spurious interrupts
PMI:          0          0          0          0   Performance monitoring
interrupts
PND:          0          0          0          0   Performance pending work
RES:       4511       9275       8470       8086   Rescheduling interrupts
CAL:       3624       8666        523       4543   Function call interrupts
TLB:        981       1111       1065       1058   TLB shootdowns
ERR:          0
MIS:          0


Regards
Mark
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