linux-kernel - Re: gettimeofday() jumping into the future

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Message-Id: <200804020726.11300.mihai.dontu@gmail.com>
Date:	Wed, 2 Apr 2008 07:26:11 +0300
From:	Mihai Donțu <mihai.dontu@...il.com>
To:	Tim Ricketts <tr@...th.li>
Cc:	Michael Smith <msmith@...h.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Wingo <wingo@...endo.com>
Subject: Re: gettimeofday() jumping into the future

On Monday 31 March 2008, Tim Ricketts wrote:
> On Thu, 23 Aug 2007, Michael Smith wrote:
> 
> > We've been seeing some strange behaviour on some of our applications
> > recently. I've tracked this down to gettimeofday() returning spurious
> > values occasionally.
> >
> > Specifically, gettimeofday() will suddenly, for a single call, return
> > a value about 4398 seconds (~1 hour 13 minutes) in the future. The
> > following call goes back to a normal value.
> 
> I have also seen this.

I don't know if gettimeofday() and dmesg's logging facility use the same
time source, but I'm seeing jumps into the past:

[   11.010300] ACPI: SSDT 3F6D3F27, 01C6 (r1  PmRef  Cpu0Cst     3001 INTL 20050624)
[    9.344283] ACPI: CPU0 (power states: C1[C1] C2[C2] C3[C3])
[    9.344528] ACPI: Processor [CPU0] (supports 8 throttling states)
[    9.344989] ACPI: SSDT 3F6D4374, 00C4 (r1  PmRef  Cpu1Ist     3000 INTL 20050624)
[    9.345458] ACPI: SSDT 3F6D40ED, 0085 (r1  PmRef  Cpu1Cst     3000 INTL 20050624)
[   11.013089] ACPI: CPU1 (power states: C1[C1] C2[C2] C3[C3])

and the future:

[   11.081332] usb 1-2: new high speed USB device using ehci_hcd and address 2
[   12.748489] usb usb4: configuration #1 chosen from 1 choice
[   12.748653] hub 4-0:1.0: USB hub found
[   12.748772] hub 4-0:1.0: 2 ports detected
[   12.849090] ACPI: PCI Interrupt 0000:00:1d.3[D] -> GSI 23 (level, low) -> IRQ 23
[   12.849338] PCI: Setting latency timer of device 0000:00:1d.3 to 64
[   12.849341] uhci_hcd 0000:00:1d.3: UHCI Host Controller
[   12.849505] uhci_hcd 0000:00:1d.3: new USB bus registered, assigned bus number 5
[   12.849734] uhci_hcd 0000:00:1d.3: irq 23, io base 0x0000bf20
[   12.850020] usb usb5: configuration #1 chosen from 1 choice
[   12.850185] hub 5-0:1.0: USB hub found
[   12.850311] hub 5-0:1.0: 2 ports detected
[   11.194688] usb 1-2: configuration #1 chosen from 1 choice

I have a 2.6.24, 64bit, SMP kernel (Intel Core 2 Duo).

-- 
Mihai Donțu
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