ia64/147501: [ia64] options PREEMPTION causes instability
marcel at FreeBSD.org
Sat Jun 5 17:00:17 UTC 2010
>Synopsis: [ia64] options PREEMPTION causes instability
>Arrival-Date: Sat Jun 05 17:00:16 UTC 2010
>Originator: Marcel Moolenaar
FreeBSD hob.lan.xcllnt.net 9.0-CURRENT FreeBSD 9.0-CURRENT #1 r208634:208809M: Sat Jun 5 08:36:47 PDT 2010 marcel at hob.lan.xcllnt.net:/usr/obj/nfs/freebsd/base/head/sys/HOB ia64
Running pho's stress2 with PREEMPTION results in kernel panics that are not seen when PREEMPTION is not enabled. This is with a SMP kernel.
On a Montecito box:
o checkout projects/stress2
o compile and run
o Wait for a panic (possibly a hard hang) within a few hours.
NOTE: Due to another bug, Montecito is the more reliable test platform.
Problem areas that are at the top of my head:
o The weak memory ordering could result in race conditions if memory fences aren't properly used
o Access to PCPU fields is non-atomic, which may result in getting the wrong field when the thread migrates to another CPU in the middle of the access sequence.
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