rcu: Add expedited grace-period support for preemptible RCU

Implement an synchronize_rcu_expedited() for preemptible RCU
that actually is expedited.  This uses
synchronize_sched_expedited() to force all threads currently
running in a preemptible-RCU read-side critical section onto the
appropriate ->blocked_tasks[] list, then takes a snapshot of all
of these lists and waits for them to drain.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1259784616158-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 1984cdc51e9..9d2c88423b3 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -157,6 +157,7 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
 {
         long gpnum;
         int level = 0;
+        int phase;
         struct rcu_node *rnp;
 
         gpnum = rsp->gpnum;
@@ -173,10 +174,13 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
                         seq_puts(m, "\n");
                         level = rnp->level;
                 }
-                seq_printf(m, "%lx/%lx %c>%c %d:%d ^%d    ",
+                phase = gpnum & 0x1;
+                seq_printf(m, "%lx/%lx %c%c>%c%c %d:%d ^%d    ",
                            rnp->qsmask, rnp->qsmaskinit,
-                           "T."[list_empty(&rnp->blocked_tasks[gpnum & 1])],
-                           "T."[list_empty(&rnp->blocked_tasks[!(gpnum & 1)])],
+                           "T."[list_empty(&rnp->blocked_tasks[phase])],
+                           "E."[list_empty(&rnp->blocked_tasks[phase + 2])],
+                           "T."[list_empty(&rnp->blocked_tasks[!phase])],
+                           "E."[list_empty(&rnp->blocked_tasks[!phase + 2])],
                            rnp->grplo, rnp->grphi, rnp->grpnum);
         }
         seq_puts(m, "\n");