Trying to test the nohz_full code, I was not able to get it to work. Finally I enabled the tick_stop tracepoint and it showed: tick_stop: success=no msg=perf events running I talked to Frederic Weisbecker about this and he informed me that perf is used by the lockup detector. I checked the code, and sure enough it is. As perf is always running when LOCKUP_DETECTOR is enabled, which will always disable nohz_full from working, instead of confusing users, disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled. When perf is changed such that it does not prevent nohz_full from working, then we can and should remove this constraint. Signed-off-by: Steven Rostedt diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 566cf2b..1364d09 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -174,6 +174,8 @@ config DEBUG_SHIRQ config LOCKUP_DETECTOR bool "Detect Hard and Soft Lockups" depends on DEBUG_KERNEL && !S390 + # Lockup detector currently prevents NO_HZ_FULL from working + depends on !NO_HZ_FULL help Say Y here to enable the kernel to act as a watchdog to detect hard and soft lockups. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/