[PATCH tip/core/rcu 06/10] rcu: Allow RCU CPU stall warnings to be off at boot, but manually enablable
in [Kernel]
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From: Paul E. McKenney on 9 Aug 2010 18:20 Currently, if RCU CPU stall warnings are enabled, they are enabled immediately upon boot. They can be manually disabled via /sys (and also re-enabled via /sys), and are automatically disabled upon panic. However, some users need RCU CPU stalls to be disabled at boot time, but to be enabled without rebuilding/rebooting. For example, someone running a real-time application in production might not want the additional latency of RCU CPU stall detection in normal operation, but might need to enable it at any point for fault isolation purposes. This commit therefore provides a new CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE kernel configuration parameter that maintains the current behavior (enable at boot) by default, but allows a kernel to be configured with RCU CPU stall detection built into the kernel, but disabled at boot time. Requested-by: Clark Williams <williams(a)redhat.com> Requested-by: John Kacur <jkacur(a)redhat.com> Signed-off-by: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com> --- kernel/rcutree.c | 2 +- kernel/rcutree.h | 6 ++++++ lib/Kconfig.debug | 13 +++++++++++++ 3 files changed, 20 insertions(+), 1 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 5d910be..5aab7da 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -144,7 +144,7 @@ module_param(qhimark, int, 0); module_param(qlowmark, int, 0); #ifdef CONFIG_RCU_CPU_STALL_DETECTOR -int rcu_cpu_stall_suppress __read_mostly; +int rcu_cpu_stall_suppress __read_mostly = RCU_CPU_STALL_SUPPRESS_INIT; module_param(rcu_cpu_stall_suppress, int, 0644); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 183ebf4..bb4d086 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -264,6 +264,12 @@ struct rcu_data { /* scheduling clock irq */ /* before ratting on them. */ +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE +#define RCU_CPU_STALL_SUPPRESS_INIT 0 +#else +#define RCU_CPU_STALL_SUPPRESS_INIT 1 +#endif + #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index af8b9c5..adfc9f1 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -832,6 +832,19 @@ config RCU_CPU_STALL_TIMEOUT RCU grace period persists, additional CPU stall warnings are printed at more widely spaced intervals. +config RCU_CPU_STALL_DETECTOR_RUNNABLE + bool "RCU CPU stall checking starts automatically at boot" + depends on RCU_CPU_STALL_DETECTOR + default y + help + If set, start checking for RCU CPU stalls immediately on + boot. Otherwise, RCU CPU stall checking must be manually + enabled. + + Say Y if you are unsure. + + Say N if you wish to suppress RCU CPU stall checking during boot. + config RCU_CPU_STALL_VERBOSE bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU -- 1.7.0.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |