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On Wed, 14 Apr 2010, Martin Shepherd wrote: > I have been experiencing hard lockups running a real-time application > under preempt-rt. Having originally had this problem while running > under 2.6.29.4-rt16, today I upgraded to 2.6.31.12-rt21, but the > problem persisted. Under both kernels, the computer simply freezes, > usually after a few hours of otherwise flawless operation. Nothing > appears on the serial console or in the system log when the system > freezes. Unfortunately, turning on the NMI watchdog stops the freezes > from occurring at all, such that I can't force an Oops that way. > > I have tried running memtest86 on the RAM, without detecting any > memory errors, and I have verified that the same problem occurs on two > different (but essentially identical) computers. > > I wonder whether there might be a clue in the fact that turning on the > NMI watchdog stops the freezes from occuring. Turning on the watchdog > unfortunately turns off tickless mode, which I need. According to the > boot-time messages, tickless is turned off because the local APIC is > non-functional (presumably because the NMI watchdog is using it). What > kind of bugs would be more likely to be seen when running under > tickless? Can you try nmi_watchdog=1 ? That keeps the tickless mode alive. > Could anybody give me any ideas on how to further debug this problem? > I have been trying to figure this out for weeks, but I haven't found > any clues. > > In case it is important, the CPU is a 1.8GHz Intel Celeron, on a > Foxconn motherboard with an Intel G31 chipset, and Intel GMA 3100 > onboard graphics. I am running the kernel (downloaded from kernel.org) > under Unbuntu 9.10. The computer also hosts two commercial digital I/O > boards, both generating interrupts, and one commercial analog I/O > board. Does the problem reproduce when you disable those boards ? Do you have the source of the drivers ? Did you ever run with lockdep enabled (CONFIG_PROVE_LOCKING=y) ? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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