Merge branch 'next' (accumulated 3.16 merge window patches) into master

Now that 3.15 is released, this merges the 'next' branch into 'master',
bringing us to the normal situation where my 'master' branch is the
merge window.

* accumulated work in next: (6809 commits)
  ufs: sb mutex merge + mutex_destroy
  powerpc: update comments for generic idle conversion
  cris: update comments for generic idle conversion
  idle: remove cpu_idle() forward declarations
  nbd: zero from and len fields in NBD_CMD_DISCONNECT.
  mm: convert some level-less printks to pr_*
  MAINTAINERS: adi-buildroot-devel is moderated
  MAINTAINERS: add linux-api for review of API/ABI changes
  mm/kmemleak-test.c: use pr_fmt for logging
  fs/dlm/debug_fs.c: replace seq_printf by seq_puts
  fs/dlm/lockspace.c: convert simple_str to kstr
  fs/dlm/config.c: convert simple_str to kstr
  mm: mark remap_file_pages() syscall as deprecated
  mm: memcontrol: remove unnecessary memcg argument from soft limit functions
  mm: memcontrol: clean up memcg zoneinfo lookup
  mm/memblock.c: call kmemleak directly from memblock_(alloc|free)
  mm/mempool.c: update the kmemleak stack trace for mempool allocations
  lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations
  mm: introduce kmemleak_update_trace()
  mm/kmemleak.c: use %u to print ->checksum
  ...

1 files changed, 228 insertions, 103 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0c47e300210..f1ba77363fb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -101,7 +101,7 @@ DEFINE_PER_CPU(struct rcu_data, sname##_data)
 RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
 RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
 
-static struct rcu_state *rcu_state;
+static struct rcu_state *rcu_state_p;
 LIST_HEAD(rcu_struct_flavors);
 
 /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
@@ -243,7 +243,7 @@ static ulong jiffies_till_next_fqs = ULONG_MAX;
 module_param(jiffies_till_first_fqs, ulong, 0644);
 module_param(jiffies_till_next_fqs, ulong, 0644);
 
-static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
+static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
 				  struct rcu_data *rdp);
 static void force_qs_rnp(struct rcu_state *rsp,
 			 int (*f)(struct rcu_data *rsp, bool *isidle,
@@ -271,6 +271,15 @@ long rcu_batches_completed_bh(void)
 EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
 
 /*
+ * Force a quiescent state.
+ */
+void rcu_force_quiescent_state(void)
+{
+	force_quiescent_state(rcu_state_p);
+}
+EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
+
+/*
  * Force a quiescent state for RCU BH.
  */
 void rcu_bh_force_quiescent_state(void)
@@ -280,6 +289,21 @@ void rcu_bh_force_quiescent_state(void)
 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
 
 /*
+ * Show the state of the grace-period kthreads.
+ */
+void show_rcu_gp_kthreads(void)
+{
+	struct rcu_state *rsp;
+
+	for_each_rcu_flavor(rsp) {
+		pr_info("%s: wait state: %d ->state: %#lx\n",
+			rsp->name, rsp->gp_state, rsp->gp_kthread->state);
+		/* sched_show_task(rsp->gp_kthread); */
+	}
+}
+EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
+
+/*
  * Record the number of times rcutorture tests have been initiated and
  * terminated.  This information allows the debugfs tracing stats to be
  * correlated to the rcutorture messages, even when the rcutorture module
@@ -294,6 +318,39 @@ void rcutorture_record_test_transition(void)
 EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
 
 /*
+ * Send along grace-period-related data for rcutorture diagnostics.
+ */
+void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
+			    unsigned long *gpnum, unsigned long *completed)
+{
+	struct rcu_state *rsp = NULL;
+
+	switch (test_type) {
+	case RCU_FLAVOR:
+		rsp = rcu_state_p;
+		break;
+	case RCU_BH_FLAVOR:
+		rsp = &rcu_bh_state;
+		break;
+	case RCU_SCHED_FLAVOR:
+		rsp = &rcu_sched_state;
+		break;
+	default:
+		break;
+	}
+	if (rsp != NULL) {
+		*flags = ACCESS_ONCE(rsp->gp_flags);
+		*gpnum = ACCESS_ONCE(rsp->gpnum);
+		*completed = ACCESS_ONCE(rsp->completed);
+		return;
+	}
+	*flags = 0;
+	*gpnum = 0;
+	*completed = 0;
+}
+EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
+
+/*
  * Record the number of writer passes through the current rcutorture test.
  * This is also used to correlate debugfs tracing stats with the rcutorture
  * messages.
@@ -324,6 +381,28 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
 }
 
 /*
+ * Return the root node of the specified rcu_state structure.
+ */
+static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
+{
+	return &rsp->node[0];
+}
+
+/*
+ * Is there any need for future grace periods?
+ * Interrupts must be disabled.  If the caller does not hold the root
+ * rnp_node structure's ->lock, the results are advisory only.
+ */
+static int rcu_future_needs_gp(struct rcu_state *rsp)
+{
+	struct rcu_node *rnp = rcu_get_root(rsp);
+	int idx = (ACCESS_ONCE(rnp->completed) + 1) & 0x1;
+	int *fp = &rnp->need_future_gp[idx];
+
+	return ACCESS_ONCE(*fp);
+}
+
+/*
  * Does the current CPU require a not-yet-started grace period?
  * The caller must have disabled interrupts to prevent races with
  * normal callback registry.
@@ -335,7 +414,7 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 
 	if (rcu_gp_in_progress(rsp))
 		return 0;  /* No, a grace period is already in progress. */
-	if (rcu_nocb_needs_gp(rsp))
+	if (rcu_future_needs_gp(rsp))
 		return 1;  /* Yes, a no-CBs CPU needs one. */
 	if (!rdp->nxttail[RCU_NEXT_TAIL])
 		return 0;  /* No, this is a no-CBs (or offline) CPU. */
@@ -350,14 +429,6 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 }
 
 /*
- * Return the root node of the specified rcu_state structure.
- */
-static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
-{
-	return &rsp->node[0];
-}
-
-/*
  * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
  *
  * If the new value of the ->dynticks_nesting counter now is zero,
@@ -387,9 +458,9 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
 	}
 	rcu_prepare_for_idle(smp_processor_id());
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
-	smp_mb__before_atomic_inc();  /* See above. */
+	smp_mb__before_atomic();  /* See above. */
 	atomic_inc(&rdtp->dynticks);
-	smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
+	smp_mb__after_atomic();  /* Force ordering with next sojourn. */
 	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 
 	/*
@@ -507,10 +578,10 @@ void rcu_irq_exit(void)
 static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
 			       int user)
 {
-	smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
+	smp_mb__before_atomic();  /* Force ordering w/previous sojourn. */
 	atomic_inc(&rdtp->dynticks);
 	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
-	smp_mb__after_atomic_inc();  /* See above. */
+	smp_mb__after_atomic();  /* See above. */
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
 	rcu_cleanup_after_idle(smp_processor_id());
 	trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
@@ -635,10 +706,10 @@ void rcu_nmi_enter(void)
 	    (atomic_read(&rdtp->dynticks) & 0x1))
 		return;
 	rdtp->dynticks_nmi_nesting++;
-	smp_mb__before_atomic_inc();  /* Force delay from prior write. */
+	smp_mb__before_atomic();  /* Force delay from prior write. */
 	atomic_inc(&rdtp->dynticks);
 	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
-	smp_mb__after_atomic_inc();  /* See above. */
+	smp_mb__after_atomic();  /* See above. */
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
 }
 
@@ -657,9 +728,9 @@ void rcu_nmi_exit(void)
 	    --rdtp->dynticks_nmi_nesting != 0)
 		return;
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
-	smp_mb__before_atomic_inc();  /* See above. */
+	smp_mb__before_atomic();  /* See above. */
 	atomic_inc(&rdtp->dynticks);
-	smp_mb__after_atomic_inc();  /* Force delay to next write. */
+	smp_mb__after_atomic();  /* Force delay to next write. */
 	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 }
 
@@ -758,7 +829,12 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
 {
 	rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
 	rcu_sysidle_check_cpu(rdp, isidle, maxj);
-	return (rdp->dynticks_snap & 0x1) == 0;
+	if ((rdp->dynticks_snap & 0x1) == 0) {
+		trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
+		return 1;
+	} else {
+		return 0;
+	}
 }
 
 /*
@@ -834,7 +910,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
 	 * we will beat on the first one until it gets unstuck, then move
 	 * to the next.  Only do this for the primary flavor of RCU.
 	 */
-	if (rdp->rsp == rcu_state &&
+	if (rdp->rsp == rcu_state_p &&
 	    ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
 		rdp->rsp->jiffies_resched += 5;
 		resched_cpu(rdp->cpu);
@@ -851,7 +927,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
 	rsp->gp_start = j;
 	smp_wmb(); /* Record start time before stall time. */
 	j1 = rcu_jiffies_till_stall_check();
-	rsp->jiffies_stall = j + j1;
+	ACCESS_ONCE(rsp->jiffies_stall) = j + j1;
 	rsp->jiffies_resched = j + j1 / 2;
 }
 
@@ -890,12 +966,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
 	/* Only let one CPU complain about others per time interval. */
 
 	raw_spin_lock_irqsave(&rnp->lock, flags);
-	delta = jiffies - rsp->jiffies_stall;
+	delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
 	if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 		return;
 	}
-	rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+	ACCESS_ONCE(rsp->jiffies_stall) = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
 	/*
@@ -932,9 +1008,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
 	print_cpu_stall_info_end();
 	for_each_possible_cpu(cpu)
 		totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
-	pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n",
+	pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n",
 	       smp_processor_id(), (long)(jiffies - rsp->gp_start),
-	       rsp->gpnum, rsp->completed, totqlen);
+	       (long)rsp->gpnum, (long)rsp->completed, totqlen);
 	if (ndetected == 0)
 		pr_err("INFO: Stall ended before state dump start\n");
 	else if (!trigger_all_cpu_backtrace())
@@ -947,12 +1023,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
 	force_quiescent_state(rsp);  /* Kick them all. */
 }
 
-/*
- * This function really isn't for public consumption, but RCU is special in
- * that context switches can allow the state machine to make progress.
- */
-extern void resched_cpu(int cpu);
-
 static void print_cpu_stall(struct rcu_state *rsp)
 {
 	int cpu;
@@ -971,14 +1041,15 @@ static void print_cpu_stall(struct rcu_state *rsp)
 	print_cpu_stall_info_end();
 	for_each_possible_cpu(cpu)
 		totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
-	pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n",
-		jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen);
+	pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n",
+		jiffies - rsp->gp_start,
+		(long)rsp->gpnum, (long)rsp->completed, totqlen);
 	if (!trigger_all_cpu_backtrace())
 		dump_stack();
 
 	raw_spin_lock_irqsave(&rnp->lock, flags);
-	if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
-		rsp->jiffies_stall = jiffies +
+	if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall)))
+		ACCESS_ONCE(rsp->jiffies_stall) = jiffies +
 				     3 * rcu_jiffies_till_stall_check() + 3;
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 
@@ -1062,7 +1133,7 @@ void rcu_cpu_stall_reset(void)
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp)
-		rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
+		ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2;
 }
 
 /*
@@ -1123,15 +1194,18 @@ static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
 /*
  * Start some future grace period, as needed to handle newly arrived
  * callbacks.  The required future grace periods are recorded in each
- * rcu_node structure's ->need_future_gp field.
+ * rcu_node structure's ->need_future_gp field.  Returns true if there
+ * is reason to awaken the grace-period kthread.
  *
  * The caller must hold the specified rcu_node structure's ->lock.
  */
-static unsigned long __maybe_unused
-rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
+static bool __maybe_unused
+rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
+		    unsigned long *c_out)
 {
 	unsigned long c;
 	int i;
+	bool ret = false;
 	struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
 
 	/*
@@ -1142,7 +1216,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
 	trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
 	if (rnp->need_future_gp[c & 0x1]) {
 		trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
-		return c;
+		goto out;
 	}
 
 	/*
@@ -1156,7 +1230,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
 	    ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) {
 		rnp->need_future_gp[c & 0x1]++;
 		trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
-		return c;
+		goto out;
 	}
 
 	/*
@@ -1197,12 +1271,15 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
 		trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot"));
 	} else {
 		trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot"));
-		rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
+		ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
 	}
 unlock_out:
 	if (rnp != rnp_root)
 		raw_spin_unlock(&rnp_root->lock);
-	return c;
+out:
+	if (c_out != NULL)
+		*c_out = c;
+	return ret;
 }
 
 /*
@@ -1226,25 +1303,43 @@ static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
 }
 
 /*
+ * Awaken the grace-period kthread for the specified flavor of RCU.
+ * Don't do a self-awaken, and don't bother awakening when there is
+ * nothing for the grace-period kthread to do (as in several CPUs
+ * raced to awaken, and we lost), and finally don't try to awaken
+ * a kthread that has not yet been created.
+ */
+static void rcu_gp_kthread_wake(struct rcu_state *rsp)
+{
+	if (current == rsp->gp_kthread ||
+	    !ACCESS_ONCE(rsp->gp_flags) ||
+	    !rsp->gp_kthread)
+		return;
+	wake_up(&rsp->gp_wq);
+}
+
+/*
  * If there is room, assign a ->completed number to any callbacks on
  * this CPU that have not already been assigned.  Also accelerate any
  * callbacks that were previously assigned a ->completed number that has
  * since proven to be too conservative, which can happen if callbacks get
  * assigned a ->completed number while RCU is idle, but with reference to
  * a non-root rcu_node structure.  This function is idempotent, so it does
- * not hurt to call it repeatedly.
+ * not hurt to call it repeatedly.  Returns an flag saying that we should
+ * awaken the RCU grace-period kthread.
  *
  * The caller must hold rnp->lock with interrupts disabled.
  */
-static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
+static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 			       struct rcu_data *rdp)
 {
 	unsigned long c;
 	int i;
+	bool ret;
 
 	/* If the CPU has no callbacks, nothing to do. */
 	if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
-		return;
+		return false;
 
 	/*
 	 * Starting from the sublist containing the callbacks most
@@ -1273,7 +1368,7 @@ static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 	 * be grouped into.
 	 */
 	if (++i >= RCU_NEXT_TAIL)
-		return;
+		return false;
 
 	/*
 	 * Assign all subsequent callbacks' ->completed number to the next
@@ -1285,13 +1380,14 @@ static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 		rdp->nxtcompleted[i] = c;
 	}
 	/* Record any needed additional grace periods. */
-	rcu_start_future_gp(rnp, rdp);
+	ret = rcu_start_future_gp(rnp, rdp, NULL);
 
 	/* Trace depending on how much we were able to accelerate. */
 	if (!*rdp->nxttail[RCU_WAIT_TAIL])
 		trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB"));
 	else
 		trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB"));
+	return ret;
 }
 
 /*
@@ -1300,17 +1396,18 @@ static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
  * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
  * sublist.  This function is idempotent, so it does not hurt to
  * invoke it repeatedly.  As long as it is not invoked -too- often...
+ * Returns true if the RCU grace-period kthread needs to be awakened.
  *
  * The caller must hold rnp->lock with interrupts disabled.
  */
-static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
+static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 			    struct rcu_data *rdp)
 {
 	int i, j;
 
 	/* If the CPU has no callbacks, nothing to do. */
 	if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
-		return;
+		return false;
 
 	/*
 	 * Find all callbacks whose ->completed numbers indicate that they
@@ -1334,26 +1431,30 @@ static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 	}
 
 	/* Classify any remaining callbacks. */
-	rcu_accelerate_cbs(rsp, rnp, rdp);
+	return rcu_accelerate_cbs(rsp, rnp, rdp);
 }
 
 /*
  * Update CPU-local rcu_data state to record the beginnings and ends of
  * grace periods.  The caller must hold the ->lock of the leaf rcu_node
  * structure corresponding to the current CPU, and must have irqs disabled.
+ * Returns true if the grace-period kthread needs to be awakened.
  */
-static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
+			      struct rcu_data *rdp)
 {
+	bool ret;
+
 	/* Handle the ends of any preceding grace periods first. */
 	if (rdp->completed == rnp->completed) {
 
 		/* No grace period end, so just accelerate recent callbacks. */
-		rcu_accelerate_cbs(rsp, rnp, rdp);
+		ret = rcu_accelerate_cbs(rsp, rnp, rdp);
 
 	} else {
 
 		/* Advance callbacks. */
-		rcu_advance_cbs(rsp, rnp, rdp);
+		ret = rcu_advance_cbs(rsp, rnp, rdp);
 
 		/* Remember that we saw this grace-period completion. */
 		rdp->completed = rnp->completed;
@@ -1372,11 +1473,13 @@ static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struc
 		rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
 		zero_cpu_stall_ticks(rdp);
 	}
+	return ret;
 }
 
 static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	unsigned long flags;
+	bool needwake;
 	struct rcu_node *rnp;
 
 	local_irq_save(flags);
@@ -1388,8 +1491,10 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
 		return;
 	}
 	smp_mb__after_unlock_lock();
-	__note_gp_changes(rsp, rnp, rdp);
+	needwake = __note_gp_changes(rsp, rnp, rdp);
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	if (needwake)
+		rcu_gp_kthread_wake(rsp);
 }
 
 /*
@@ -1403,12 +1508,12 @@ static int rcu_gp_init(struct rcu_state *rsp)
 	rcu_bind_gp_kthread();
 	raw_spin_lock_irq(&rnp->lock);
 	smp_mb__after_unlock_lock();
-	if (rsp->gp_flags == 0) {
+	if (!ACCESS_ONCE(rsp->gp_flags)) {
 		/* Spurious wakeup, tell caller to go back to sleep.  */
 		raw_spin_unlock_irq(&rnp->lock);
 		return 0;
 	}
-	rsp->gp_flags = 0; /* Clear all flags: New grace period. */
+	ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */
 
 	if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
 		/*
@@ -1453,7 +1558,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 		WARN_ON_ONCE(rnp->completed != rsp->completed);
 		ACCESS_ONCE(rnp->completed) = rsp->completed;
 		if (rnp == rdp->mynode)
-			__note_gp_changes(rsp, rnp, rdp);
+			(void)__note_gp_changes(rsp, rnp, rdp);
 		rcu_preempt_boost_start_gp(rnp);
 		trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
 					    rnp->level, rnp->grplo,
@@ -1501,7 +1606,7 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
 	if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
 		raw_spin_lock_irq(&rnp->lock);
 		smp_mb__after_unlock_lock();
-		rsp->gp_flags &= ~RCU_GP_FLAG_FQS;
+		ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS;
 		raw_spin_unlock_irq(&rnp->lock);
 	}
 	return fqs_state;
@@ -1513,6 +1618,7 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
 static void rcu_gp_cleanup(struct rcu_state *rsp)
 {
 	unsigned long gp_duration;
+	bool needgp = false;
 	int nocb = 0;
 	struct rcu_data *rdp;
 	struct rcu_node *rnp = rcu_get_root(rsp);
@@ -1548,7 +1654,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 		ACCESS_ONCE(rnp->completed) = rsp->gpnum;
 		rdp = this_cpu_ptr(rsp->rda);
 		if (rnp == rdp->mynode)
-			__note_gp_changes(rsp, rnp, rdp);
+			needgp = __note_gp_changes(rsp, rnp, rdp) || needgp;
 		/* smp_mb() provided by prior unlock-lock pair. */
 		nocb += rcu_future_gp_cleanup(rsp, rnp);
 		raw_spin_unlock_irq(&rnp->lock);
@@ -1564,9 +1670,10 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 	trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end"));
 	rsp->fqs_state = RCU_GP_IDLE;
 	rdp = this_cpu_ptr(rsp->rda);
-	rcu_advance_cbs(rsp, rnp, rdp);  /* Reduce false positives below. */
-	if (cpu_needs_another_gp(rsp, rdp)) {
-		rsp->gp_flags = RCU_GP_FLAG_INIT;
+	/* Advance CBs to reduce false positives below. */
+	needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp;
+	if (needgp || cpu_needs_another_gp(rsp, rdp)) {
+		ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
 		trace_rcu_grace_period(rsp->name,
 				       ACCESS_ONCE(rsp->gpnum),
 				       TPS("newreq"));
@@ -1593,6 +1700,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
 			trace_rcu_grace_period(rsp->name,
 					       ACCESS_ONCE(rsp->gpnum),
 					       TPS("reqwait"));
+			rsp->gp_state = RCU_GP_WAIT_GPS;
 			wait_event_interruptible(rsp->gp_wq,
 						 ACCESS_ONCE(rsp->gp_flags) &
 						 RCU_GP_FLAG_INIT);
@@ -1620,6 +1728,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
 			trace_rcu_grace_period(rsp->name,
 					       ACCESS_ONCE(rsp->gpnum),
 					       TPS("fqswait"));
+			rsp->gp_state = RCU_GP_WAIT_FQS;
 			ret = wait_event_interruptible_timeout(rsp->gp_wq,
 					((gf = ACCESS_ONCE(rsp->gp_flags)) &
 					 RCU_GP_FLAG_FQS) ||
@@ -1665,14 +1774,6 @@ static int __noreturn rcu_gp_kthread(void *arg)
 	}
 }
 
-static void rsp_wakeup(struct irq_work *work)
-{
-	struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
-
-	/* Wake up rcu_gp_kthread() to start the grace period. */
-	wake_up(&rsp->gp_wq);
-}
-
 /*
  * Start a new RCU grace period if warranted, re-initializing the hierarchy
  * in preparation for detecting the next grace period.  The caller must hold
@@ -1681,8 +1782,10 @@ static void rsp_wakeup(struct irq_work *work)
  * Note that it is legal for a dying CPU (which is marked as offline) to
  * invoke this function.  This can happen when the dying CPU reports its
  * quiescent state.
+ *
+ * Returns true if the grace-period kthread must be awakened.
  */
-static void
+static bool
 rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
 		      struct rcu_data *rdp)
 {
@@ -1693,20 +1796,18 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
 		 * or a grace period is already in progress.
 		 * Either way, don't start a new grace period.
 		 */
-		return;
+		return false;
 	}
-	rsp->gp_flags = RCU_GP_FLAG_INIT;
+	ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
 	trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
 			       TPS("newreq"));
 
 	/*
 	 * We can't do wakeups while holding the rnp->lock, as that
 	 * could cause possible deadlocks with the rq->lock. Defer
-	 * the wakeup to interrupt context.  And don't bother waking
-	 * up the running kthread.
+	 * the wakeup to our caller.
 	 */
-	if (current != rsp->gp_kthread)
-		irq_work_queue(&rsp->wakeup_work);
+	return true;
 }
 
 /*
@@ -1715,12 +1816,14 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
  * is invoked indirectly from rcu_advance_cbs(), which would result in
  * endless recursion -- or would do so if it wasn't for the self-deadlock
  * that is encountered beforehand.
+ *
+ * Returns true if the grace-period kthread needs to be awakened.
  */
-static void
-rcu_start_gp(struct rcu_state *rsp)
+static bool rcu_start_gp(struct rcu_state *rsp)
 {
 	struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
 	struct rcu_node *rnp = rcu_get_root(rsp);
+	bool ret = false;
 
 	/*
 	 * If there is no grace period in progress right now, any
@@ -1730,8 +1833,9 @@ rcu_start_gp(struct rcu_state *rsp)
 	 * resulting in pointless grace periods.  So, advance callbacks
 	 * then start the grace period!
 	 */
-	rcu_advance_cbs(rsp, rnp, rdp);
-	rcu_start_gp_advanced(rsp, rnp, rdp);
+	ret = rcu_advance_cbs(rsp, rnp, rdp) || ret;
+	ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret;
+	return ret;
 }
 
 /*
@@ -1820,6 +1924,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	unsigned long flags;
 	unsigned long mask;
+	bool needwake;
 	struct rcu_node *rnp;
 
 	rnp = rdp->mynode;
@@ -1848,9 +1953,11 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 		 * This GP can't end until cpu checks in, so all of our
 		 * callbacks can be processed during the next GP.
 		 */
-		rcu_accelerate_cbs(rsp, rnp, rdp);
+		needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
 
 		rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
+		if (needwake)
+			rcu_gp_kthread_wake(rsp);
 	}
 }
 
@@ -1951,7 +2058,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
 static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
 {
 	int i;
-	struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
+	struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
 
 	/* No-CBs CPUs are handled specially. */
 	if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
@@ -2320,7 +2427,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
 		raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
 		return;  /* Someone beat us to it. */
 	}
-	rsp->gp_flags |= RCU_GP_FLAG_FQS;
+	ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS;
 	raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
 	wake_up(&rsp->gp_wq);  /* Memory barrier implied by wake_up() path. */
 }
@@ -2334,7 +2441,8 @@ static void
 __rcu_process_callbacks(struct rcu_state *rsp)
 {
 	unsigned long flags;
-	struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
+	bool needwake;
+	struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
 
 	WARN_ON_ONCE(rdp->beenonline == 0);
 
@@ -2345,8 +2453,10 @@ __rcu_process_callbacks(struct rcu_state *rsp)
 	local_irq_save(flags);
 	if (cpu_needs_another_gp(rsp, rdp)) {
 		raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
-		rcu_start_gp(rsp);
+		needwake = rcu_start_gp(rsp);
 		raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
+		if (needwake)
+			rcu_gp_kthread_wake(rsp);
 	} else {
 		local_irq_restore(flags);
 	}
@@ -2404,6 +2514,8 @@ static void invoke_rcu_core(void)
 static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 			    struct rcu_head *head, unsigned long flags)
 {
+	bool needwake;
+
 	/*
 	 * If called from an extended quiescent state, invoke the RCU
 	 * core in order to force a re-evaluation of RCU's idleness.
@@ -2433,8 +2545,10 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 
 			raw_spin_lock(&rnp_root->lock);
 			smp_mb__after_unlock_lock();
-			rcu_start_gp(rsp);
+			needwake = rcu_start_gp(rsp);
 			raw_spin_unlock(&rnp_root->lock);
+			if (needwake)
+				rcu_gp_kthread_wake(rsp);
 		} else {
 			/* Give the grace period a kick. */
 			rdp->blimit = LONG_MAX;
@@ -2537,6 +2651,20 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 EXPORT_SYMBOL_GPL(call_rcu_bh);
 
 /*
+ * Queue an RCU callback for lazy invocation after a grace period.
+ * This will likely be later named something like "call_rcu_lazy()",
+ * but this change will require some way of tagging the lazy RCU
+ * callbacks in the list of pending callbacks. Until then, this
+ * function may only be called from __kfree_rcu().
+ */
+void kfree_call_rcu(struct rcu_head *head,
+		    void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, rcu_state_p, -1, 1);
+}
+EXPORT_SYMBOL_GPL(kfree_call_rcu);
+
+/*
  * Because a context switch is a grace period for RCU-sched and RCU-bh,
  * any blocking grace-period wait automatically implies a grace period
  * if there is only one CPU online at any point time during execution
@@ -2659,7 +2787,7 @@ unsigned long get_state_synchronize_rcu(void)
 	 * time-consuming work between get_state_synchronize_rcu()
 	 * and cond_synchronize_rcu().
 	 */
-	return smp_load_acquire(&rcu_state->gpnum);
+	return smp_load_acquire(&rcu_state_p->gpnum);
 }
 EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
 
@@ -2685,7 +2813,7 @@ void cond_synchronize_rcu(unsigned long oldstate)
 	 * Ensure that this load happens before any RCU-destructive
 	 * actions the caller might carry out after we return.
 	 */
-	newstate = smp_load_acquire(&rcu_state->completed);
+	newstate = smp_load_acquire(&rcu_state_p->completed);
 	if (ULONG_CMP_GE(oldstate, newstate))
 		synchronize_rcu();
 }
@@ -2790,7 +2918,7 @@ void synchronize_sched_expedited(void)
 		s = atomic_long_read(&rsp->expedited_done);
 		if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
 			/* ensure test happens before caller kfree */
-			smp_mb__before_atomic_inc(); /* ^^^ */
+			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone1);
 			return;
 		}
@@ -2808,7 +2936,7 @@ void synchronize_sched_expedited(void)
 		s = atomic_long_read(&rsp->expedited_done);
 		if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
 			/* ensure test happens before caller kfree */
-			smp_mb__before_atomic_inc(); /* ^^^ */
+			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone2);
 			return;
 		}
@@ -2837,7 +2965,7 @@ void synchronize_sched_expedited(void)
 		s = atomic_long_read(&rsp->expedited_done);
 		if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
 			/* ensure test happens before caller kfree */
-			smp_mb__before_atomic_inc(); /* ^^^ */
+			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_done_lost);
 			break;
 		}
@@ -2988,7 +3116,7 @@ static void rcu_barrier_callback(struct rcu_head *rhp)
 static void rcu_barrier_func(void *type)
 {
 	struct rcu_state *rsp = type;
-	struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
+	struct rcu_data *rdp = raw_cpu_ptr(rsp->rda);
 
 	_rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
 	atomic_inc(&rsp->barrier_cpu_count);
@@ -3160,7 +3288,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
  * that this CPU cannot possibly have any RCU callbacks in flight yet.
  */
 static void
-rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
+rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
 {
 	unsigned long flags;
 	unsigned long mask;
@@ -3173,7 +3301,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
 	/* Set up local state, ensuring consistent view of global state. */
 	raw_spin_lock_irqsave(&rnp->lock, flags);
 	rdp->beenonline = 1;	 /* We have now been online. */
-	rdp->preemptible = preemptible;
 	rdp->qlen_last_fqs_check = 0;
 	rdp->n_force_qs_snap = rsp->n_force_qs;
 	rdp->blimit = blimit;
@@ -3217,8 +3344,7 @@ static void rcu_prepare_cpu(int cpu)
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp)
-		rcu_init_percpu_data(cpu, rsp,
-				     strcmp(rsp->name, "rcu_preempt") == 0);
+		rcu_init_percpu_data(cpu, rsp);
 }
 
 /*
@@ -3228,7 +3354,7 @@ static int rcu_cpu_notify(struct notifier_block *self,
 				    unsigned long action, void *hcpu)
 {
 	long cpu = (long)hcpu;
-	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
+	struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
 	struct rcu_node *rnp = rdp->mynode;
 	struct rcu_state *rsp;
 
@@ -3402,8 +3528,8 @@ static void __init rcu_init_one(struct rcu_state *rsp,
 			rnp->qsmaskinit = 0;
 			rnp->grplo = j * cpustride;
 			rnp->grphi = (j + 1) * cpustride - 1;
-			if (rnp->grphi >= NR_CPUS)
-				rnp->grphi = NR_CPUS - 1;
+			if (rnp->grphi >= nr_cpu_ids)
+				rnp->grphi = nr_cpu_ids - 1;
 			if (i == 0) {
 				rnp->grpnum = 0;
 				rnp->grpmask = 0;
@@ -3422,7 +3548,6 @@ static void __init rcu_init_one(struct rcu_state *rsp,
 
 	rsp->rda = rda;
 	init_waitqueue_head(&rsp->gp_wq);
-	init_irq_work(&rsp->wakeup_work, rsp_wakeup);
 	rnp = rsp->level[rcu_num_lvls - 1];
 	for_each_possible_cpu(i) {
 		while (i > rnp->grphi)