Messages in this thread | | | From | (Eric W. Biederman) | Date | Wed, 29 Feb 2012 10:07:00 -0800 | Subject | Re: Hang on "echo b > /proc/sysrq-trigger" |
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Keith Chew <keith.chew@gmail.com> writes:
> Hi > > To test the reliability of a hardware, I have a script which reboots a > machine every 15 minutes after boot up. This machine has a dual video > output, VGA and DVI-D, both driven via an intel GM45 chipset (I am > using kernel 2.6.39.24 kernel intel drivers). > > Some interesting results (which can be reproduced consistently): > "echo b > /proc/sysrq-trigger" via DVI-D - after 2-3 days, it hangs > (freezes) before reboot (dmesg only shows "Resetting...", nothing
My blind guess would be that it is the BIOS on the machine that is hung.
> after that, no panic, stack trace, etc) > "echo b > /proc/sysrq-trigger" via VGA - runs > 1 week > "reboot -fn" via VGA or DVI-D - runs > 1 week > "reboot" via VGA or DVI-D - runs > 1 week > > I suspect that the intel graphics driver is not happy with the "echo b >> /proc/sysrq-trigger" when it is still running. > > I would like to make the "echo b" successfully reboot the machine, but > this would appear to be a hardware bug? Is there anything that can be > done in the kernel to make the "echo b" successfully work 100%?
echo b > /proc/sysrq-trigger triggers the emergency_restart path which tries but skips some steps so that it has a reasonable chance of working when the kernel is wedged, it looks like some of those steps it skips are needed on your hardware.
Eric
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