rcu: Rework synchronize_sched_expedited() counter handling

Now that synchronize_sched_expedited() have a mutex, it can use simpler
work-already-done detection scheme.  This commit simplifies this scheme
by using something similar to the sequence-locking counter scheme.
A counter is incremented before and after each grace period, so that
the counter is odd in the midst of the grace period and even otherwise.
So if the counter has advanced to the second even number that is
greater than or equal to the snapshot, the required grace period has
already happened.

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

1 files changed, 4 insertions, 8 deletions

diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index 3ea7ffc7d5c4..a1ab3a5f6290 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -185,18 +185,14 @@ static int show_rcuexp(struct seq_file *m, void *v)
 {
         struct rcu_state *rsp = (struct rcu_state *)m->private;
 
-        seq_printf(m, "s=%lu d=%lu w=%lu tf=%lu wd1=%lu wd2=%lu n=%lu sc=%lu dt=%lu dl=%lu dx=%lu\n",
-                   atomic_long_read(&rsp->expedited_start),
-                   atomic_long_read(&rsp->expedited_done),
-                   atomic_long_read(&rsp->expedited_wrap),
+        seq_printf(m, "t=%lu tf=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu sc=%lu\n",
+                   rsp->expedited_sequence,
                    atomic_long_read(&rsp->expedited_tryfail),
                    atomic_long_read(&rsp->expedited_workdone1),
                    atomic_long_read(&rsp->expedited_workdone2),
+                   rsp->expedited_workdone3,
                    atomic_long_read(&rsp->expedited_normal),
-                   atomic_long_read(&rsp->expedited_stoppedcpus),
-                   atomic_long_read(&rsp->expedited_done_tries),
-                   atomic_long_read(&rsp->expedited_done_lost),
-                   atomic_long_read(&rsp->expedited_done_exit));
+                   rsp->expedited_sequence / 2);
         return 0;
 }