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Date: Tue, 19 Aug 2008 05:49:23 -0700 (PDT) From: David Witbrodt <dawitbro@...global.net> To: Ingo Molnar <mingo@...e.hu> Cc: Yinghai Lu <yhlu.kernel@...il.com>, linux-kernel@...r.kernel.org, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, netdev <netdev@...r.kernel.org> Subject: Re: HPET regression in 2.6.26 versus 2.6.25 -- connection between HPET and lockups found > Just to make sure: on a working kernel, do you get the HPET messages? > I.e. does the hpet truly work in that case? On the "fileserver", where 2.6.25 works but 2.6.26 locks up, the HPET _does_ work on a working kernel: $ uname -r 2.6.26.revert1 $ dmesg | grep -i hpet ACPI: HPET 77FE80C0, 0038 (r1 RS690 AWRDACPI 42302E31 AWRD 98) ACPI: HPET id: 0x10b9a201 base: 0xfed00000 hpet clockevent registered hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0 hpet0: 4 32-bit timers, 14318180 Hz hpet_resources: 0xfed00000 is busy What I didn't realize is that the "desktop" machine, where 2.6.26 has always "worked", does NOT have a working HPET after all, even though I have enabled all HPET options in .config: $ uname -r 2.6.26.080801.desktop.uvesafb $ dmesg | grep -i hpet $ This means I misunderstood my situation on "desktop". I believed HPET was working on all of my machines, but now I am not certain that it ever worked on "desktop" since I built it (May 2007). The question never arose before, and because I enabled the HPET option in .config, I just assumed that HPET was working. (Duh...) I failed to look into this until now. At any rate, my subject line is still accurate: there _is_ an HPET regression on "fileserver" (and "webserver"), since it worked on 2.6.25 kernels but causes lockups on 2.6.2[67] kernels. (I don't know what is going on with "desktop": does the motherboard lack HPET, or does the Linux kernel not support the HPET hardware on the motherboard?) BTW: the 'dmesg' output above is the same on "desktop" with 2.6.25 and 2.6.26 -- I just checked to be sure. For "fileserver", I checked an old 2.6.25 kernel just now, and the output is identical. Another experiment: I just tried this... static __init int hpet_insert_resource(void) { - if (!hpet_res) + /* if (!hpet_res) */ return 1; - return insert_resource(&iomem_resource, hpet_res); + /* return insert_resource(&iomem_resource, hpet_res); */ } ... and the lock up still occurs. So, the memory is allocated but the resource info is not inserted into the tree. Whether the dynamic memory for hpet_res is being damaged or not has no bearing on the lockups, it would seem. Looks like I was barking up the wrong tree.... Dave W. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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