rcu: make CPU stall warning timeout configurable

Also set the default to 60 seconds, up from the previous hard-coded timeout
of 10 seconds.  This allows people who care to set short timeouts, while
avoiding people with unusual configurations (make randconfig!!!) from being
bothered with spurious CPU stall warnings.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 5ce197e87792ccfaf0c5a7e27cfa61acc6466309..183ebf40531585ebbd8e0230ce666b42672a7b74 100644 (file)
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -254,9 +254,10 @@ struct rcu_data {
 #define RCU_STALL_DELAY_DELTA         0
 #endif
 
-#define RCU_SECONDS_TILL_STALL_CHECK   (10 * HZ + RCU_STALL_DELAY_DELTA)
+#define RCU_SECONDS_TILL_STALL_CHECK   (CONFIG_RCU_CPU_STALL_TIMEOUT * HZ + \
+                                       RCU_STALL_DELAY_DELTA)
                                                /* for rsp->jiffies_stall */
-#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ + RCU_STALL_DELAY_DELTA)
+#define RCU_SECONDS_TILL_STALL_RECHECK (3 * RCU_SECONDS_TILL_STALL_CHECK + 30)
                                                /* for rsp->jiffies_stall */
 #define RCU_STALL_RAT_DELAY            2       /* Allow other CPUs time */
                                                /*  to take at least one */

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 12465f2ef76623ae0250e658f9f73373d37d1461..b5005b7621032cd7f9a12b749e301a750e550397 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -845,6 +845,17 @@ config RCU_CPU_STALL_DETECTOR
 
          Say Y if you are unsure.
 
+config RCU_CPU_STALL_TIMEOUT
+       int "RCU CPU stall timeout in seconds"
+       depends on RCU_CPU_STALL_DETECTOR
+       range 3 300
+       default 60
+       help
+         If a given RCU grace period extends more than the specified
+         number of seconds, a CPU stall warning is printed.  If the
+         RCU grace period persists, additional CPU stall warnings are
+         printed at more widely spaced intervals.
+
 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