rcu: Add more information to the wrong-idle-task complaint

The current code just complains if the current task is not the idle task.
This commit therefore adds printing of the identity of the idle task.

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

2 files changed, 20 insertions, 4 deletions

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 9b9bdf666fb5..6d70ff71a875 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -65,10 +65,14 @@ static void rcu_idle_enter_common(long long oldval)
         }
         RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
         if (!idle_cpu(smp_processor_id())) {
-                WARN_ON_ONCE(1);        /* must be idle task! */
+                struct task_struct *idle = idle_task(smp_processor_id());
+
                 RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
                                             oldval, rcu_dynticks_nesting));
                 ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
         }
         rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
 }
@@ -115,10 +119,14 @@ static void rcu_idle_exit_common(long long oldval)
         }
         RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
         if (!idle_cpu(smp_processor_id())) {
-                WARN_ON_ONCE(1);        /* must be idle task! */
+                struct task_struct *idle = idle_task(smp_processor_id());
+
                 RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
                           oldval, rcu_dynticks_nesting));
                 ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
         }
 }
 
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 06e40dd53b23..9888a0ad2d4e 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -356,10 +356,14 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
         }
         trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
         if (!idle_cpu(smp_processor_id())) {
-                WARN_ON_ONCE(1);        /* must be idle task! */
+                struct task_struct *idle = idle_task(smp_processor_id());
+
                 trace_rcu_dyntick("Error on entry: not idle task",
                                    oldval, rdtp->dynticks_nesting);
                 ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
         }
         /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
         smp_mb__before_atomic_inc();  /* See above. */
@@ -445,10 +449,14 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
         WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
         trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
         if (!idle_cpu(smp_processor_id())) {
-                WARN_ON_ONCE(1);        /* must be idle task! */
+                struct task_struct *idle = idle_task(smp_processor_id());
+
                 trace_rcu_dyntick("Error on exit: not idle task",
                                   oldval, rdtp->dynticks_nesting);
                 ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
         }
 }