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Date: Wed, 23 Dec 2009 07:10:49 -0800
From: "Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To: "markh@...pro.net" <markh@...pro.net>
CC: "dmarkh@....rr.com" <dmarkh@....rr.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Alain Knaff <alain@...ff.lu>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"fdutils@...tils.linux.lu" <fdutils@...tils.linux.lu>,
"Li, Shaohua" <shaohua.li@...el.com>, Ingo Molnar <mingo@...e.hu>
Subject: RE: [Fdutils] DMA cache consistency bug introduced in 2.6.28 (Was:
Re: Cannot format floppies under kernel 2.6.*?)
>-----Original Message-----
>From: Mark Hounschell [mailto:markh@...pro.net]
>Sent: Wednesday, December 23, 2009 5:03 AM
>To: Pallipadi, Venkatesh
>Cc: dmarkh@....rr.com; Linus Torvalds; Alain Knaff; Linux
>Kernel Mailing List; fdutils@...tils.linux.lu; Li, Shaohua; Ingo Molnar
>Subject: Re: [Fdutils] DMA cache consistency bug introduced in
>2.6.28 (Was: Re: Cannot format floppies under kernel 2.6.*?)
>
>On 12/22/2009 07:22 PM, Mark Hounschell wrote:
>> On 12/22/2009 06:37 PM, Pallipadi, Venkatesh wrote:
>>> On Tue, 2009-12-22 at 09:57 -0800, Mark Hounschell wrote:
>>>> On 12/22/2009 12:38 PM, Linus Torvalds wrote:
>>>>>
>>>>> [ Ingo, Venki and Shaohua added to cc: see the whole
>thread on lkml for
>>>>> details, but Mark is basically chasing down a situation
>where the floppy
>>>>> driver seems to have trouble formatting floppies, and
>it happened
>>>>> between 2.6.27 and .28. The trouble seems to be that a
>DMA transfer of a
>>>>> memory block transfers the wrong value for the first
>byte of the block.
>>>>>
>>>>> Which should be impossible, but whatever. Some part of
>the system has a
>>>>> cached buffer that isn't flushed.
>>>>>
>>>>> What gets _you_ guys involved is that Mark cannot
>reproduce the bug if
>>>>> HPET is disabled in the BIOS or by using 'nohpet'. He
>found that out by
>>>>> pure luck while bisecting, because some time during his
>bisect, his
>>>>> machine wouldn't even boot with HPET.
>>>>>
>>>>> So the problem is: with HPET enabled, 2.6.27.4 _used_
>to work. But
>>>>> 2.6.28 (and current -git) does not. Any ideas? ]
>>>>>
>>>>> On Tue, 22 Dec 2009, Mark Hounschell wrote:
>>>>>>
>>>>>> 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>
>>>>>>
>>>>>> 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.
>>>>>
>>>>> Ok, so we know why HPET didn't boot for you, and that was
>fixed later (by
>>>>> that 5ceb1a04). But is this also when the floppy started
>mis-behaving?
>>>>>
>>>>
>>>> Commit 26afe5f2fbf06ea0765aaa316640c4dd472310c0 is when
>the floppy stops
>>>> working
>>>> and also when I could no longer boot with hpet enabled.
>>>
>>>
>>> I am missing something here. Commit 26afe5f2 is where
>system does not
>>> boot with HPET or is it where the floppy stops working when you boot
>>> with HPET enabled.
>>>
>>
>> As it happens, both happen there. Commit 5ceb1a04 is where it starts
>> booting _again_ with hpet enabled. So I took that patch
>(5ceb1a04) and
>> applied it to (26afe5f2f) to be able to boot with hpet
>enabled. I had to
>> use the quiet option to get to a login prompt, but there is where the
>> floppy format first fails, just as it does in 2.6.28 and up.
>>
>>> Can you try "idle=halt" with both .27 and .28 with /proc/interrupts
>>> output in each case. With that option, we should be using local APIC
>>> timer and PIT, HPET or HPET with MSI should not really
>matter. Does it
>>> still fail with .28 with that option?
>>>
>
>2.6.28 still fails with that option.
>
>2.6.27.41 /proc/interrupts with idle=halt
>
> CPU0 CPU1 CPU2 CPU3
> 0: 126 0 0 1
>IO-APIC-edge timer
> 1: 0 0 1 157
>IO-APIC-edge i8042
> 3: 0 0 0 6 IO-APIC-edge
> 4: 0 0 0 6 IO-APIC-edge
> 6: 0 0 0 4
>IO-APIC-edge floppy
> 8: 0 0 0 1
>IO-APIC-edge rtc0
> 9: 0 0 0 0
>IO-APIC-fasteoi acpi
> 12: 0 0 1 128
>IO-APIC-edge i8042
> 14: 0 0 34 4457 IO-APIC-edge
>pata_atiixp
> 15: 0 0 4 480 IO-APIC-edge
>pata_atiixp
> 16: 0 0 0 397 IO-APIC-fasteoi
>aic79xx, ohci_hcd:usb3, ohci_hcd:usb4, HDA Intel
> 17: 0 0 0 2 IO-APIC-fasteoi
>ehci_hcd:usb1
> 18: 0 0 0 0 IO-APIC-fasteoi
>ohci_hcd:usb5, ohci_hcd:usb6, ohci_hcd:usb7
> 19: 0 0 0 142 IO-APIC-fasteoi
>aic7xxx, ehci_hcd:usb2, ttySLG0, eth1
> 22: 0 0 4 1154
>IO-APIC-fasteoi ahci
>219: 0 0 3 63
>PCI-MSI-edge eth0
>NMI: 0 0 0 0
>Non-maskable interrupts
>LOC: 91539 91964 92525 91181 Local timer
>interrupts
>RES: 2888 3873 2434 2721
>Rescheduling interrupts
>CAL: 240 245 247 84 function
>call interrupts
>TLB: 768 628 526 512 TLB shootdowns
>SPU: 0 0 0 0 Spurious interrupts
>ERR: 0
>MIS: 0
>
>2.6.28 /proc/interrupts with idle=halt
>
> CPU0 CPU1 CPU2 CPU3
> 0: 126 0 2 0
>IO-APIC-edge timer
> 1: 0 0 192 0
>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 1 0
>IO-APIC-edge rtc0
> 9: 0 0 0 0
>IO-APIC-fasteoi acpi
> 12: 0 0 128 1
>IO-APIC-edge i8042
> 14: 0 1 147114 396 IO-APIC-edge
>pata_atiixp
> 15: 0 0 646 2 IO-APIC-edge
>pata_atiixp
> 16: 0 0 396 0 IO-APIC-fasteoi
>aic79xx, ohci_hcd:usb2, ohci_hcd:usb4, HDA Intel
> 17: 0 0 0 0 IO-APIC-fasteoi
>ehci_hcd:usb1
> 18: 0 0 0 0 IO-APIC-fasteoi
>ohci_hcd:usb5, ohci_hcd:usb6, ohci_hcd:usb7
> 19: 0 0 362 1 IO-APIC-fasteoi
>aic7xxx, ehci_hcd:usb3, ttySLG0, eth1
> 22: 0 0 874 1
>IO-APIC-fasteoi ahci
>1274: 0 0 193 4
>PCI-MSI-edge eth0
>1279: 513207 0 0 0
>HPET_MSI-edge hpet2
>NMI: 0 0 0 0
>Non-maskable interrupts
>LOC: 268 513395 513138 522088 Local timer
>interrupts
>RES: 3262 3679 2573 3746
>Rescheduling interrupts
>CAL: 131 166 57 147 Function
>call interrupts
>TLB: 680 438 450 639 TLB shootdowns
>SPU: 0 0 0 0 Spurious interrupts
>ERR: 0
>MIS: 0
>
Hmm. Looks like hpet2 is still getting used instead of local APIC timer in .28 case.
I was expecting some low number in hpet2 and local timer on all CPU to be around the same value. Above shows CPU 0 is depending on hpet2 for some reason even with idle=halt. Can you send the output of below two in case of .28
/proc/timer_list
grep . /sys/devices/system/cpu/cpu0/cpuidle/*/*
Thanks,
Venki
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