rcu: Provide RCU CPU stall warnings for tiny RCU

[firefly-linux-kernel-4.4.55.git] / kernel / rcutiny_plugin.h

diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index f85016a2309b94c08121f0e3346c1c24d81d4c18..8a233002faeba228d6195481f0812af703b7e9f3 100644 (file)
--- 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 */