1 files changed, 149 insertions, 29 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8b41bd13cc3d..77198911b8dd 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -126,6 +126,18 @@ static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
 	.lock	= INIT_LOCAL_LOCK(softirq_ctrl.lock),
 };
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key bh_lock_key;
+struct lockdep_map bh_lock_map = {
+	.name			= "local_bh",
+	.key			= &bh_lock_key,
+	.wait_type_outer	= LD_WAIT_FREE,
+	.wait_type_inner	= LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
+	.lock_type		= LD_LOCK_PERCPU,
+};
+EXPORT_SYMBOL_GPL(bh_lock_map);
+#endif
+
 /**
  * local_bh_blocked() - Check for idle whether BH processing is blocked
  *
@@ -148,10 +160,16 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 
 	WARN_ON_ONCE(in_hardirq());
 
+	lock_map_acquire_read(&bh_lock_map);
+
 	/* First entry of a task into a BH disabled section? */
 	if (!current->softirq_disable_cnt) {
 		if (preemptible()) {
-			local_lock(&softirq_ctrl.lock);
+			if (IS_ENABLED(CONFIG_PREEMPT_RT_NEEDS_BH_LOCK))
+				local_lock(&softirq_ctrl.lock);
+			else
+				migrate_disable();
+
 			/* Required to meet the RCU bottomhalf requirements. */
 			rcu_read_lock();
 		} else {
@@ -163,17 +181,34 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 	 * Track the per CPU softirq disabled state. On RT this is per CPU
 	 * state to allow preemption of bottom half disabled sections.
 	 */
-	newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt);
-	/*
-	 * Reflect the result in the task state to prevent recursion on the
-	 * local lock and to make softirq_count() & al work.
-	 */
-	current->softirq_disable_cnt = newcnt;
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_NEEDS_BH_LOCK)) {
+		newcnt = this_cpu_add_return(softirq_ctrl.cnt, cnt);
+		/*
+		 * Reflect the result in the task state to prevent recursion on the
+		 * local lock and to make softirq_count() & al work.
+		 */
+		current->softirq_disable_cnt = newcnt;
 
-	if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
-		raw_local_irq_save(flags);
-		lockdep_softirqs_off(ip);
-		raw_local_irq_restore(flags);
+		if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
+			raw_local_irq_save(flags);
+			lockdep_softirqs_off(ip);
+			raw_local_irq_restore(flags);
+		}
+	} else {
+		bool sirq_dis = false;
+
+		if (!current->softirq_disable_cnt)
+			sirq_dis = true;
+
+		this_cpu_add(softirq_ctrl.cnt, cnt);
+		current->softirq_disable_cnt += cnt;
+		WARN_ON_ONCE(current->softirq_disable_cnt < 0);
+
+		if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && sirq_dis) {
+			raw_local_irq_save(flags);
+			lockdep_softirqs_off(ip);
+			raw_local_irq_restore(flags);
+		}
 	}
 }
 EXPORT_SYMBOL(__local_bh_disable_ip);
@@ -181,23 +216,42 @@ EXPORT_SYMBOL(__local_bh_disable_ip);
 static void __local_bh_enable(unsigned int cnt, bool unlock)
 {
 	unsigned long flags;
+	bool sirq_en = false;
 	int newcnt;
 
-	DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
-			    this_cpu_read(softirq_ctrl.cnt));
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_NEEDS_BH_LOCK)) {
+		DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
+				    this_cpu_read(softirq_ctrl.cnt));
+		if (softirq_count() == cnt)
+			sirq_en = true;
+	} else {
+		if (current->softirq_disable_cnt == cnt)
+			sirq_en = true;
+	}
 
-	if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) {
+	if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && sirq_en) {
 		raw_local_irq_save(flags);
 		lockdep_softirqs_on(_RET_IP_);
 		raw_local_irq_restore(flags);
 	}
 
-	newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt);
-	current->softirq_disable_cnt = newcnt;
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_NEEDS_BH_LOCK)) {
+		newcnt = this_cpu_sub_return(softirq_ctrl.cnt, cnt);
+		current->softirq_disable_cnt = newcnt;
 
-	if (!newcnt && unlock) {
-		rcu_read_unlock();
-		local_unlock(&softirq_ctrl.lock);
+		if (!newcnt && unlock) {
+			rcu_read_unlock();
+			local_unlock(&softirq_ctrl.lock);
+		}
+	} else {
+		current->softirq_disable_cnt -= cnt;
+		this_cpu_sub(softirq_ctrl.cnt, cnt);
+		if (unlock && !current->softirq_disable_cnt) {
+			migrate_enable();
+			rcu_read_unlock();
+		} else {
+			WARN_ON_ONCE(current->softirq_disable_cnt < 0);
+		}
 	}
 }
 
@@ -211,8 +265,13 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 	WARN_ON_ONCE(in_hardirq());
 	lockdep_assert_irqs_enabled();
 
+	lock_map_release(&bh_lock_map);
+
 	local_irq_save(flags);
-	curcnt = __this_cpu_read(softirq_ctrl.cnt);
+	if (IS_ENABLED(CONFIG_PREEMPT_RT_NEEDS_BH_LOCK))
+		curcnt = this_cpu_read(softirq_ctrl.cnt);
+	else
+		curcnt = current->softirq_disable_cnt;
 
 	/*
 	 * If this is not reenabling soft interrupts, no point in trying to
@@ -261,6 +320,8 @@ static inline void ksoftirqd_run_begin(void)
 /* Counterpart to ksoftirqd_run_begin() */
 static inline void ksoftirqd_run_end(void)
 {
+	/* pairs with the lock_map_acquire_read() in ksoftirqd_run_begin() */
+	lock_map_release(&bh_lock_map);
 	__local_bh_enable(SOFTIRQ_OFFSET, true);
 	WARN_ON_ONCE(in_interrupt());
 	local_irq_enable();
@@ -280,17 +341,24 @@ static inline void invoke_softirq(void)
 		wakeup_softirqd();
 }
 
+#define SCHED_SOFTIRQ_MASK	BIT(SCHED_SOFTIRQ)
+
 /*
  * flush_smp_call_function_queue() can raise a soft interrupt in a function
- * call. On RT kernels this is undesired and the only known functionality
- * in the block layer which does this is disabled on RT. If soft interrupts
- * get raised which haven't been raised before the flush, warn so it can be
+ * call. On RT kernels this is undesired and the only known functionalities
+ * are in the block layer which is disabled on RT, and in the scheduler for
+ * idle load balancing. If soft interrupts get raised which haven't been
+ * raised before the flush, warn if it is not a SCHED_SOFTIRQ so it can be
  * investigated.
  */
 void do_softirq_post_smp_call_flush(unsigned int was_pending)
 {
-	if (WARN_ON_ONCE(was_pending != local_softirq_pending()))
+	unsigned int is_pending = local_softirq_pending();
+
+	if (unlikely(was_pending != is_pending)) {
+		WARN_ON_ONCE(was_pending != (is_pending & ~SCHED_SOFTIRQ_MASK));
 		invoke_softirq();
+	}
 }
 
 #else /* CONFIG_PREEMPT_RT */
@@ -780,6 +848,58 @@ static bool tasklet_clear_sched(struct tasklet_struct *t)
 	return false;
 }
 
+#ifdef CONFIG_PREEMPT_RT
+struct tasklet_sync_callback {
+	spinlock_t	cb_lock;
+	atomic_t	cb_waiters;
+};
+
+static DEFINE_PER_CPU(struct tasklet_sync_callback, tasklet_sync_callback) = {
+	.cb_lock	= __SPIN_LOCK_UNLOCKED(tasklet_sync_callback.cb_lock),
+	.cb_waiters	= ATOMIC_INIT(0),
+};
+
+static void tasklet_lock_callback(void)
+{
+	spin_lock(this_cpu_ptr(&tasklet_sync_callback.cb_lock));
+}
+
+static void tasklet_unlock_callback(void)
+{
+	spin_unlock(this_cpu_ptr(&tasklet_sync_callback.cb_lock));
+}
+
+static void tasklet_callback_cancel_wait_running(void)
+{
+	struct tasklet_sync_callback *sync_cb = this_cpu_ptr(&tasklet_sync_callback);
+
+	atomic_inc(&sync_cb->cb_waiters);
+	spin_lock(&sync_cb->cb_lock);
+	atomic_dec(&sync_cb->cb_waiters);
+	spin_unlock(&sync_cb->cb_lock);
+}
+
+static void tasklet_callback_sync_wait_running(void)
+{
+	struct tasklet_sync_callback *sync_cb = this_cpu_ptr(&tasklet_sync_callback);
+
+	if (atomic_read(&sync_cb->cb_waiters)) {
+		spin_unlock(&sync_cb->cb_lock);
+		spin_lock(&sync_cb->cb_lock);
+	}
+}
+
+#else /* !CONFIG_PREEMPT_RT: */
+
+static void tasklet_lock_callback(void) { }
+static void tasklet_unlock_callback(void) { }
+static void tasklet_callback_sync_wait_running(void) { }
+
+#ifdef CONFIG_SMP
+static void tasklet_callback_cancel_wait_running(void) { }
+#endif
+#endif /* !CONFIG_PREEMPT_RT */
+
 static void tasklet_action_common(struct tasklet_head *tl_head,
 				  unsigned int softirq_nr)
 {
@@ -791,6 +911,7 @@ static void tasklet_action_common(struct tasklet_head *tl_head,
 	tl_head->tail = &tl_head->head;
 	local_irq_enable();
 
+	tasklet_lock_callback();
 	while (list) {
 		struct tasklet_struct *t = list;
 
@@ -810,6 +931,7 @@ static void tasklet_action_common(struct tasklet_head *tl_head,
 					}
 				}
 				tasklet_unlock(t);
+				tasklet_callback_sync_wait_running();
 				continue;
 			}
 			tasklet_unlock(t);
@@ -822,6 +944,7 @@ static void tasklet_action_common(struct tasklet_head *tl_head,
 		__raise_softirq_irqoff(softirq_nr);
 		local_irq_enable();
 	}
+	tasklet_unlock_callback();
 }
 
 static __latent_entropy void tasklet_action(void)
@@ -872,12 +995,9 @@ void tasklet_unlock_spin_wait(struct tasklet_struct *t)
 			/*
 			 * Prevent a live lock when current preempted soft
 			 * interrupt processing or prevents ksoftirqd from
-			 * running. If the tasklet runs on a different CPU
-			 * then this has no effect other than doing the BH
-			 * disable/enable dance for nothing.
+			 * running.
 			 */
-			local_bh_disable();
-			local_bh_enable();
+			tasklet_callback_cancel_wait_running();
 		} else {
 			cpu_relax();
 		}