8 files changed, 130 insertions, 51 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 7d30240e5bfe..a5e90e139ba5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -486,6 +486,14 @@ config PREEMPT_RCU
           This option enables preemptible-RCU code that is common between
           the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 
+config RCU_STALL_COMMON
+        def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
+        help
+          This option enables RCU CPU stall code that is common between
+          the TINY and TREE variants of RCU.  The purpose is to allow
+          the tiny variants to disable RCU CPU stall warnings, while
+          making these warnings mandatory for the tree variants.
+
 config CONTEXT_TRACKING
        bool
 
diff --git a/kernel/rcu.h b/kernel/rcu.h
index 20dfba576c2b..7f8e7590e3e5 100644
--- a/kernel/rcu.h
+++ b/kernel/rcu.h
@@ -111,4 +111,11 @@ static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
 
 extern int rcu_expedited;
 
+#ifdef CONFIG_RCU_STALL_COMMON
+
+extern int rcu_cpu_stall_suppress;
+int rcu_jiffies_till_stall_check(void);
+
+#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
+
 #endif /* __LINUX_RCU_H */
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index a2cf76177b44..076730d95acc 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -412,3 +412,54 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
 #else
 #define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
 #endif
+
+#ifdef CONFIG_RCU_STALL_COMMON
+
+#ifdef CONFIG_PROVE_RCU
+#define RCU_STALL_DELAY_DELTA          (5 * HZ)
+#else
+#define RCU_STALL_DELAY_DELTA          0
+#endif
+
+int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
+int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
+
+module_param(rcu_cpu_stall_suppress, int, 0644);
+module_param(rcu_cpu_stall_timeout, int, 0644);
+
+int rcu_jiffies_till_stall_check(void)
+{
+        int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
+
+        /*
+         * Limit check must be consistent with the Kconfig limits
+         * for CONFIG_RCU_CPU_STALL_TIMEOUT.
+         */
+        if (till_stall_check < 3) {
+                ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
+                till_stall_check = 3;
+        } else if (till_stall_check > 300) {
+                ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
+                till_stall_check = 300;
+        }
+        return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
+}
+
+static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
+{
+        rcu_cpu_stall_suppress = 1;
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block rcu_panic_block = {
+        .notifier_call = rcu_panic,
+};
+
+static int __init check_cpu_stall_init(void)
+{
+        atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
+        return 0;
+}
+early_initcall(check_cpu_stall_init);
+
+#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index e7dce58f9c2a..b899df317edc 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -51,10 +51,10 @@ static void __call_rcu(struct rcu_head *head,
                        void (*func)(struct rcu_head *rcu),
                        struct rcu_ctrlblk *rcp);
 
-#include "rcutiny_plugin.h"
-
 static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
 
+#include "rcutiny_plugin.h"
+
 /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
 static void rcu_idle_enter_common(long long newval)
 {
@@ -205,6 +205,7 @@ int rcu_is_cpu_rrupt_from_idle(void)
  */
 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 {
+        reset_cpu_stall_ticks(rcp);
         if (rcp->rcucblist != NULL &&
             rcp->donetail != rcp->curtail) {
                 rcp->donetail = rcp->curtail;
@@ -251,6 +252,7 @@ void rcu_bh_qs(int cpu)
  */
 void rcu_check_callbacks(int cpu, int user)
 {
+        check_cpu_stalls();
         if (user || rcu_is_cpu_rrupt_from_idle())
                 rcu_sched_qs(cpu);
         else if (!in_softirq())
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index f85016a2309b..8a233002faeb 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -33,6 +33,9 @@ struct rcu_ctrlblk {
         struct rcu_head **donetail;     /* ->next pointer of last "done" CB. */
         struct rcu_head **curtail;      /* ->next pointer of last CB. */
         RCU_TRACE(long qlen);           /* Number of pending CBs. */
+        RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
+        RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
+        RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
         RCU_TRACE(char *name);          /* Name of RCU type. */
 };
 
@@ -54,6 +57,51 @@ int rcu_scheduler_active __read_mostly;
 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+#ifdef CONFIG_RCU_TRACE
+
+static void check_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+        unsigned long j;
+        unsigned long js;
+
+        if (rcu_cpu_stall_suppress)
+                return;
+        rcp->ticks_this_gp++;
+        j = jiffies;
+        js = rcp->jiffies_stall;
+        if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
+                pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
+                       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
+                       jiffies - rcp->gp_start, rcp->qlen);
+                dump_stack();
+        }
+        if (*rcp->curtail && ULONG_CMP_GE(j, js))
+                rcp->jiffies_stall = jiffies +
+                        3 * rcu_jiffies_till_stall_check() + 3;
+        else if (ULONG_CMP_GE(j, js))
+                rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+}
+
+static void check_cpu_stall_preempt(void);
+
+#endif /* #ifdef CONFIG_RCU_TRACE */
+
+static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
+{
+#ifdef CONFIG_RCU_TRACE
+        rcp->ticks_this_gp = 0;
+        rcp->gp_start = jiffies;
+        rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+#endif /* #ifdef CONFIG_RCU_TRACE */
+}
+
+static void check_cpu_stalls(void)
+{
+        RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
+        RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
+        RCU_TRACE(check_cpu_stall_preempt());
+}
+
 #ifdef CONFIG_TINY_PREEMPT_RCU
 
 #include <linux/delay.h>
@@ -448,6 +496,7 @@ static void rcu_preempt_start_gp(void)
                 /* Official start of GP. */
                 rcu_preempt_ctrlblk.gpnum++;
                 RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
+                reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb);
 
                 /* Any blocked RCU readers block new GP. */
                 if (rcu_preempt_blocked_readers_any())
@@ -1054,4 +1103,11 @@ MODULE_AUTHOR("Paul E. McKenney");
 MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
 MODULE_LICENSE("GPL");
 
+static void check_cpu_stall_preempt(void)
+{
+#ifdef CONFIG_TINY_PREEMPT_RCU
+        check_cpu_stall(&rcu_preempt_ctrlblk.rcb);
+#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */
+}
+
 #endif /* #ifdef CONFIG_RCU_TRACE */
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e441b77b614e..d069430f0974 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -217,12 +217,6 @@ module_param(blimit, long, 0444);
 module_param(qhimark, long, 0444);
 module_param(qlowmark, long, 0444);
 
-int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
-int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
-
-module_param(rcu_cpu_stall_suppress, int, 0644);
-module_param(rcu_cpu_stall_timeout, int, 0644);
-
 static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
 static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
 
@@ -793,28 +787,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
         return 0;
 }
 
-static int jiffies_till_stall_check(void)
-{
-        int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
-
-        /*
-         * Limit check must be consistent with the Kconfig limits
-         * for CONFIG_RCU_CPU_STALL_TIMEOUT.
-         */
-        if (till_stall_check < 3) {
-                ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
-                till_stall_check = 3;
-        } else if (till_stall_check > 300) {
-                ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
-                till_stall_check = 300;
-        }
-        return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
-}
-
 static void record_gp_stall_check_time(struct rcu_state *rsp)
 {
         rsp->gp_start = jiffies;
-        rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
+        rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
 }
 
 /*
@@ -857,7 +833,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
         }
-        rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
+        rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
         /*
@@ -935,7 +911,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
         raw_spin_lock_irqsave(&rnp->lock, flags);
         if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
                 rsp->jiffies_stall = jiffies +
-                                     3 * jiffies_till_stall_check() + 3;
+                                     3 * rcu_jiffies_till_stall_check() + 3;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
         set_need_resched();  /* kick ourselves to get things going. */
@@ -966,12 +942,6 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
         }
 }
 
-static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
-{
-        rcu_cpu_stall_suppress = 1;
-        return NOTIFY_DONE;
-}
-
 /**
  * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
  *
@@ -989,15 +959,6 @@ void rcu_cpu_stall_reset(void)
                 rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
 }
 
-static struct notifier_block rcu_panic_block = {
-        .notifier_call = rcu_panic,
-};
-
-static void __init check_cpu_stall_init(void)
-{
-        atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
-}
-
 /*
  * Update CPU-local rcu_data state to record the newly noticed grace period.
  * This is used both when we started the grace period and when we notice
@@ -3074,7 +3035,6 @@ void __init rcu_init(void)
         cpu_notifier(rcu_cpu_notify, 0);
         for_each_online_cpu(cpu)
                 rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
-        check_cpu_stall_init();
 }
 
 #include "rcutree_plugin.h"
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4b69291b093d..db9bec83fe3f 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -343,11 +343,6 @@ struct rcu_data {
 
 #define RCU_JIFFIES_TILL_FORCE_QS        3      /* for rsp->jiffies_force_qs */
 
-#ifdef CONFIG_PROVE_RCU
-#define RCU_STALL_DELAY_DELTA          (5 * HZ)
-#else
-#define RCU_STALL_DELAY_DELTA          0
-#endif
 #define RCU_STALL_RAT_DELAY             2       /* Allow other CPUs time */
                                                 /*  to take at least one */
                                                 /*  scheduling clock irq */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3a353091a903..f7329b3d4c8d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -970,7 +970,7 @@ config RCU_TORTURE_TEST_RUNNABLE
 
 config RCU_CPU_STALL_TIMEOUT
         int "RCU CPU stall timeout in seconds"
-        depends on TREE_RCU || TREE_PREEMPT_RCU
+        depends on RCU_STALL_COMMON
         range 3 300
         default 21
         help