rcu/tasks: Add detailed grace-period and barrier diagnostics

This commit adds rcu_tasks_torture_stats_print(),
rcu_tasks_trace_torture_stats_print(), and
rcu_tasks_rude_torture_stats_print() functions that provide detailed
diagnostics on grace-period, callback, and barrier state.

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 31e679c7110eb4e9832738c80321006e5138ea53..17463e95b6efff620cafba22c6b31d55246fc776 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -164,6 +164,7 @@ static inline void rcu_nocb_flush_deferred_wakeup(void) { }
        } while (0)
 void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func);
 void synchronize_rcu_tasks(void);
+void rcu_tasks_torture_stats_print(char *tt, char *tf);
 # else
 # define rcu_tasks_classic_qs(t, preempt) do { } while (0)
 # define call_rcu_tasks call_rcu
@@ -190,6 +191,7 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
                        rcu_tasks_trace_qs_blkd(t);                             \
                }                                                               \
        } while (0)
+void rcu_tasks_trace_torture_stats_print(char *tt, char *tf);
 # else
 # define rcu_tasks_trace_qs(t) do { } while (0)
 # endif
@@ -202,6 +204,7 @@ do {                                                                        \
 
 # ifdef CONFIG_TASKS_RUDE_RCU
 void synchronize_rcu_tasks_rude(void);
+void rcu_tasks_rude_torture_stats_print(char *tt, char *tf);
 # endif
 
 #define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t, false)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index d44abcd656d6cf123bfc3836029bddbab42f7204..5f6d80ce1e47a50d3aa52cf1ad75811c6ba32450 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -714,9 +714,7 @@ static void __init rcu_tasks_bootup_oddness(void)
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 }
 
-#endif /* #ifndef CONFIG_TINY_RCU */
 
-#ifndef CONFIG_TINY_RCU
 /* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
 static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
 {
@@ -750,6 +748,52 @@ static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
                rtp->lazy_jiffies,
                s);
 }
+
+/* Dump out more rcutorture-relevant state common to all RCU-tasks flavors. */
+static void rcu_tasks_torture_stats_print_generic(struct rcu_tasks *rtp, char *tt,
+                                                 char *tf, char *tst)
+{
+       cpumask_var_t cm;
+       int cpu;
+       bool gotcb = false;
+       unsigned long j = jiffies;
+
+       pr_alert("%s%s Tasks%s RCU g%ld gp_start %lu gp_jiffies %lu gp_state %d (%s).\n",
+                tt, tf, tst, data_race(rtp->tasks_gp_seq),
+                j - data_race(rtp->gp_start), j - data_race(rtp->gp_jiffies),
+                data_race(rtp->gp_state), tasks_gp_state_getname(rtp));
+       pr_alert("\tEnqueue shift %d limit %d Dequeue limit %d gpseq %lu.\n",
+                data_race(rtp->percpu_enqueue_shift),
+                data_race(rtp->percpu_enqueue_lim),
+                data_race(rtp->percpu_dequeue_lim),
+                data_race(rtp->percpu_dequeue_gpseq));
+       (void)zalloc_cpumask_var(&cm, GFP_KERNEL);
+       pr_alert("\tCallback counts:");
+       for_each_possible_cpu(cpu) {
+               long n;
+               struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+               if (cpumask_available(cm) && !rcu_barrier_cb_is_done(&rtpcp->barrier_q_head))
+                       cpumask_set_cpu(cpu, cm);
+               n = rcu_segcblist_n_cbs(&rtpcp->cblist);
+               if (!n)
+                       continue;
+               pr_cont(" %d:%ld", cpu, n);
+               gotcb = true;
+       }
+       if (gotcb)
+               pr_cont(".\n");
+       else
+               pr_cont(" (none).\n");
+       pr_alert("\tBarrier seq %lu count %d holdout CPUs ",
+                data_race(rtp->barrier_q_seq), atomic_read(&rtp->barrier_q_count));
+       if (cpumask_available(cm) && !cpumask_empty(cm))
+               pr_cont(" %*pbl.\n", cpumask_pr_args(cm));
+       else
+               pr_cont("(none).\n");
+       free_cpumask_var(cm);
+}
+
 #endif // #ifndef CONFIG_TINY_RCU
 
 static void exit_tasks_rcu_finish_trace(struct task_struct *t);
@@ -1201,6 +1245,12 @@ void show_rcu_tasks_classic_gp_kthread(void)
        show_rcu_tasks_generic_gp_kthread(&rcu_tasks, "");
 }
 EXPORT_SYMBOL_GPL(show_rcu_tasks_classic_gp_kthread);
+
+void rcu_tasks_torture_stats_print(char *tt, char *tf)
+{
+       rcu_tasks_torture_stats_print_generic(&rcu_tasks, tt, tf, "");
+}
+EXPORT_SYMBOL_GPL(rcu_tasks_torture_stats_print);
 #endif // !defined(CONFIG_TINY_RCU)
 
 struct task_struct *get_rcu_tasks_gp_kthread(void)
@@ -1361,6 +1411,12 @@ void show_rcu_tasks_rude_gp_kthread(void)
        show_rcu_tasks_generic_gp_kthread(&rcu_tasks_rude, "");
 }
 EXPORT_SYMBOL_GPL(show_rcu_tasks_rude_gp_kthread);
+
+void rcu_tasks_rude_torture_stats_print(char *tt, char *tf)
+{
+       rcu_tasks_torture_stats_print_generic(&rcu_tasks_rude, tt, tf, "");
+}
+EXPORT_SYMBOL_GPL(rcu_tasks_rude_torture_stats_print);
 #endif // !defined(CONFIG_TINY_RCU)
 
 struct task_struct *get_rcu_tasks_rude_gp_kthread(void)
@@ -2038,6 +2094,12 @@ void show_rcu_tasks_trace_gp_kthread(void)
        show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
 }
 EXPORT_SYMBOL_GPL(show_rcu_tasks_trace_gp_kthread);
+
+void rcu_tasks_trace_torture_stats_print(char *tt, char *tf)
+{
+       rcu_tasks_torture_stats_print_generic(&rcu_tasks_trace, tt, tf, "");
+}
+EXPORT_SYMBOL_GPL(rcu_tasks_trace_torture_stats_print);
 #endif // !defined(CONFIG_TINY_RCU)
 
 struct task_struct *get_rcu_tasks_trace_gp_kthread(void)