rcu: Instrument synchronize_rcu_expedited() for debugfs tracing

This commit adds the counters to rcu_state and updates them in
synchronize_rcu_expedited() to provide the data needed for debugfs
tracing.

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

2 files changed, 24 insertions, 3 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3c72e5e5528c..b966d56ebb51 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -2321,6 +2321,7 @@ void synchronize_sched_expedited(void)
                          (ulong)atomic_long_read(&rsp->expedited_done) +
                          ULONG_MAX / 8)) {
                 synchronize_sched();
+                atomic_long_inc(&rsp->expedited_wrap);
                 return;
         }
 
@@ -2341,11 +2342,14 @@ void synchronize_sched_expedited(void)
                              synchronize_sched_expedited_cpu_stop,
                              NULL) == -EAGAIN) {
                 put_online_cpus();
+                atomic_long_inc(&rsp->expedited_tryfail);
 
                 /* Check to see if someone else did our work for us. */
                 s = atomic_long_read(&rsp->expedited_done);
                 if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
-                        smp_mb(); /* ensure test happens before caller kfree */
+                        /* ensure test happens before caller kfree */
+                        smp_mb__before_atomic_inc(); /* ^^^ */
+                        atomic_long_inc(&rsp->expedited_workdone1);
                         return;
                 }
 
@@ -2354,13 +2358,16 @@ void synchronize_sched_expedited(void)
                         udelay(trycount * num_online_cpus());
                 } else {
                         synchronize_sched();
+                        atomic_long_inc(&rsp->expedited_normal);
                         return;
                 }
 
                 /* Recheck to see if someone else did our work for us. */
                 s = atomic_long_read(&rsp->expedited_done);
                 if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
-                        smp_mb(); /* ensure test happens before caller kfree */
+                        /* ensure test happens before caller kfree */
+                        smp_mb__before_atomic_inc(); /* ^^^ */
+                        atomic_long_inc(&rsp->expedited_workdone2);
                         return;
                 }
 
@@ -2375,6 +2382,7 @@ void synchronize_sched_expedited(void)
                 snap = atomic_long_read(&rsp->expedited_start);
                 smp_mb(); /* ensure read is before try_stop_cpus(). */
         }
+        atomic_long_inc(&rsp->expedited_stoppedcpus);
 
         /*
          * Everyone up to our most recent fetch is covered by our grace
@@ -2383,12 +2391,16 @@ void synchronize_sched_expedited(void)
          * than we did already did their update.
          */
         do {
+                atomic_long_inc(&rsp->expedited_done_tries);
                 s = atomic_long_read(&rsp->expedited_done);
                 if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
-                        smp_mb(); /* ensure test happens before caller kfree */
+                        /* ensure test happens before caller kfree */
+                        smp_mb__before_atomic_inc(); /* ^^^ */
+                        atomic_long_inc(&rsp->expedited_done_lost);
                         break;
                 }
         } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s);
+        atomic_long_inc(&rsp->expedited_done_exit);
 
         put_online_cpus();
 }
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 88f3d9d5971d..d274af357210 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -406,6 +406,15 @@ struct rcu_state {
 
         atomic_long_t expedited_start;          /* Starting ticket. */
         atomic_long_t expedited_done;           /* Done ticket. */
+        atomic_long_t expedited_wrap;           /* # near-wrap incidents. */
+        atomic_long_t expedited_tryfail;        /* # acquisition failures. */
+        atomic_long_t expedited_workdone1;      /* # done by others #1. */
+        atomic_long_t expedited_workdone2;      /* # done by others #2. */
+        atomic_long_t expedited_normal;         /* # fallbacks to normal. */
+        atomic_long_t expedited_stoppedcpus;    /* # successful stop_cpus. */
+        atomic_long_t expedited_done_tries;     /* # tries to update _done. */
+        atomic_long_t expedited_done_lost;      /* # times beaten to _done. */
+        atomic_long_t expedited_done_exit;      /* # times exited _done loop. */
 
         unsigned long jiffies_force_qs;         /* Time at which to invoke */
                                                 /*  force_quiescent_state(). */