Turn on CONFIG_HAVE_UNSTABLE_SCHED_CLOCK for SGI_SN. SGI Altix has unsynchronized itc clocks. This results in rq->clock occasionally being set to a time in the past by a remote cpu. Note that it is possible that this problem may exist for other ia64 machines as well, based on the following comment for sched_clock() in arch/ia64/kernel/head.S: * Return a CPU-local timestamp in nano-seconds. This timestamp is * NOT synchronized across CPUs its return value must never be * compared against the values returned on another CPU. The usage in * kernel/sched.c ensures that. Signed-off-by: Dimitri Sivanich <sivanich@xxxxxxx> --- Greg, if everyone is OK with this patch, this should also be applied to all stable trees starting with 2.6.26. arch/ia64/Kconfig | 1 + 1 file changed, 1 insertion(+) Index: linux-2.6/arch/ia64/Kconfig =================================================================== --- linux-2.6.orig/arch/ia64/Kconfig 2009-01-06 10:13:13.051918923 -0600 +++ linux-2.6/arch/ia64/Kconfig 2009-01-06 10:13:44.547856328 -0600 @@ -536,6 +536,7 @@ config IA64_MC_ERR_INJECT config SGI_SN def_bool y if (IA64_SGI_SN2 || IA64_GENERIC) + select HAVE_UNSTABLE_SCHED_CLOCK config IA64_ESI bool "ESI (Extensible SAL Interface) support" -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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