rcu: Use simple wait queues where possible in rcutree

As of commit dae6e64d2bcfd ("rcu: Introduce proper blocking to no-CBs kthreads
GP waits") the RCU subsystem started making use of wait queues.

Here we convert all additions of RCU wait queues to use simple wait queues,
since they don't need the extra overhead of the full wait queue features.

Originally this was done for RT kernels[1], since we would get things like...

  BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
  in_atomic(): 1, irqs_disabled(): 1, pid: 8, name: rcu_preempt
  Pid: 8, comm: rcu_preempt Not tainted
  Call Trace:
   [<ffffffff8106c8d0>] __might_sleep+0xd0/0xf0
   [<ffffffff817d77b4>] rt_spin_lock+0x24/0x50
   [<ffffffff8106fcf6>] __wake_up+0x36/0x70
   [<ffffffff810c4542>] rcu_gp_kthread+0x4d2/0x680
   [<ffffffff8105f910>] ? __init_waitqueue_head+0x50/0x50
   [<ffffffff810c4070>] ? rcu_gp_fqs+0x80/0x80
   [<ffffffff8105eabb>] kthread+0xdb/0xe0
   [<ffffffff8106b912>] ? finish_task_switch+0x52/0x100
   [<ffffffff817e0754>] kernel_thread_helper+0x4/0x10
   [<ffffffff8105e9e0>] ? __init_kthread_worker+0x60/0x60
   [<ffffffff817e0750>] ? gs_change+0xb/0xb

...and hence simple wait queues were deployed on RT out of necessity
(as simple wait uses a raw lock), but mainline might as well take
advantage of the more streamline support as well.

[1] This is a carry forward of work from v3.10-rt; the original conversion
was by Thomas on an earlier -rt version, and Sebastian extended it to
additional post-3.10 added RCU waiters; here I've added a commit log and
unified the RCU changes into one, and uprev'd it to match mainline RCU.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-6-git-send-email-wagi@monom.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 13 insertions, 13 deletions

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 631aff61abe9..080bd202d360 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1811,9 +1811,9 @@ early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
  * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
  * grace period.
  */
-static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
 {
-	wake_up_all(sq);
+	swake_up_all(sq);
 }
 
 /*
@@ -1829,15 +1829,15 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
 	rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
 }
 
-static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
 {
 	return &rnp->nocb_gp_wq[rnp->completed & 0x1];
 }
 
 static void rcu_init_one_nocb(struct rcu_node *rnp)
 {
-	init_waitqueue_head(&rnp->nocb_gp_wq[0]);
-	init_waitqueue_head(&rnp->nocb_gp_wq[1]);
+	init_swait_queue_head(&rnp->nocb_gp_wq[0]);
+	init_swait_queue_head(&rnp->nocb_gp_wq[1]);
 }
 
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
@@ -1862,7 +1862,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
 	if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {
 		/* Prior smp_mb__after_atomic() orders against prior enqueue. */
 		WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);
-		wake_up(&rdp_leader->nocb_wq);
+		swake_up(&rdp_leader->nocb_wq);
 	}
 }
 
@@ -2074,7 +2074,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
 	 */
 	trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait"));
 	for (;;) {
-		wait_event_interruptible(
+		swait_event_interruptible(
 			rnp->nocb_gp_wq[c & 0x1],
 			(d = ULONG_CMP_GE(READ_ONCE(rnp->completed), c)));
 		if (likely(d))
@@ -2102,7 +2102,7 @@ wait_again:
 	/* Wait for callbacks to appear. */
 	if (!rcu_nocb_poll) {
 		trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
-		wait_event_interruptible(my_rdp->nocb_wq,
+		swait_event_interruptible(my_rdp->nocb_wq,
 				!READ_ONCE(my_rdp->nocb_leader_sleep));
 		/* Memory barrier handled by smp_mb() calls below and repoll. */
 	} else if (firsttime) {
@@ -2177,7 +2177,7 @@ wait_again:
 			 * List was empty, wake up the follower.
 			 * Memory barriers supplied by atomic_long_add().
 			 */
-			wake_up(&rdp->nocb_wq);
+			swake_up(&rdp->nocb_wq);
 		}
 	}
 
@@ -2198,7 +2198,7 @@ static void nocb_follower_wait(struct rcu_data *rdp)
 		if (!rcu_nocb_poll) {
 			trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
 					    "FollowerSleep");
-			wait_event_interruptible(rdp->nocb_wq,
+			swait_event_interruptible(rdp->nocb_wq,
 						 READ_ONCE(rdp->nocb_follower_head));
 		} else if (firsttime) {
 			/* Don't drown trace log with "Poll"! */
@@ -2357,7 +2357,7 @@ void __init rcu_init_nohz(void)
 static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
 {
 	rdp->nocb_tail = &rdp->nocb_head;
-	init_waitqueue_head(&rdp->nocb_wq);
+	init_swait_queue_head(&rdp->nocb_wq);
 	rdp->nocb_follower_tail = &rdp->nocb_follower_head;
 }
 
@@ -2507,7 +2507,7 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
 	return false;
 }
 
-static void rcu_nocb_gp_cleanup(wait_queue_head_t *sq)
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
 {
 }
 
@@ -2515,7 +2515,7 @@ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
 {
 }
 
-static wait_queue_head_t *rcu_nocb_gp_get(struct rcu_node *rnp)
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
 {
 	return NULL;
 }