Messages in this thread | | | Date | Mon, 28 May 2007 10:54:43 +0900 | From | Satoru Takeuchi <> | Subject | CPU hotplug: system hang on CPU hot remove during `pfmon --system-wide' |
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Hi,
I found a bug on CPU hotplug. If `pfmon --system-wide' is running, CPU hot remove causes system hang. On the other hand, CPU hot add during that command seems to work fine.
I detected this problem on my ia64 box, and I don't know that this problem is also occur on any arch or freezer based CPU hotplug. Since I'm investigating this problem now, I'm glad if someone reports the test result on other arch or freezer.
Currently I don't know anything about the cause of this problem.
How To Reproduce ================
Assuming you have two terminal, named term A and term B.
1) execute pfmon from term A
$ pfmon --system-wide <press ENTER to stop session>
2) issue CPU hot remove from term B
# echo 0 >/sys/devices/system/cpu/cpu1/online
3) Press enter from term B
Expected Result ===============
Succeed to offline CPU
Actual Result =============
System hang occurs and there are the following messages on serial console.
------------------------------------------------------------------------------- CPU0 1925600 CPU_CYCLES CPU1 could not stop monitoring, CPU may be offline, check results pfm_write_old_pmds error [3] Device or resource busy pfmon_read_pmds error Device or resource busy CPU1 read_results error -------------------------------------------------------------------------------
Thanks,
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