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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org
Subject: [GIT pull] irq/urgent for v5.18-rc6
References: <165201148069.536527.1960632033331546251.tglx@xen13>
Message-ID: <165201148219.536527.2201418994305067142.tglx@xen13>
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Date:   Sun,  8 May 2022 14:05:21 +0200 (CEST)
Precedence: bulk

Linus,

please pull the latest irq/urgent branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq-urgent-2022-=
05-08

up to:  8707898e22fd: genirq: Synchronize interrupt thread startup


A fix for the threaded interrupt core. A quick sequence of
request/free_irq() can result in a hang because the interrupt thread did
not reach the thread function and got stopped in the kthread core
already. That leaves a state active counter arround which makes a
invocation of synchronized_irq() on that interrupt hang forever. Ensure
that the thread reached the thread function in request_irq() to prevent
that.

Thanks,

	tglx

------------------>
Thomas Pfaff (1):
      genirq: Synchronize interrupt thread startup


 kernel/irq/internals.h |  2 ++
 kernel/irq/irqdesc.c   |  2 ++
 kernel/irq/manage.c    | 39 +++++++++++++++++++++++++++++----------
 3 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 99cbdf55a8bd..f09c60393e55 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -29,12 +29,14 @@ extern struct irqaction chained_action;
  * IRQTF_WARNED    - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed
  * IRQTF_AFFINITY  - irq thread is requested to adjust affinity
  * IRQTF_FORCED_THREAD  - irq action is force threaded
+ * IRQTF_READY     - signals that irq thread is ready
  */
 enum {
 	IRQTF_RUNTHREAD,
 	IRQTF_WARNED,
 	IRQTF_AFFINITY,
 	IRQTF_FORCED_THREAD,
+	IRQTF_READY,
 };
=20
 /*
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 939d21cd55c3..0099b87dd853 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -407,6 +407,7 @@ static struct irq_desc *alloc_desc(int irq, int node, uns=
igned int flags,
 	lockdep_set_class(&desc->lock, &irq_desc_lock_class);
 	mutex_init(&desc->request_mutex);
 	init_rcu_head(&desc->rcu);
+	init_waitqueue_head(&desc->wait_for_threads);
=20
 	desc_set_defaults(irq, desc, node, affinity, owner);
 	irqd_set(&desc->irq_data, flags);
@@ -575,6 +576,7 @@ int __init early_irq_init(void)
 		raw_spin_lock_init(&desc[i].lock);
 		lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
 		mutex_init(&desc[i].request_mutex);
+		init_waitqueue_head(&desc[i].wait_for_threads);
 		desc_set_defaults(i, &desc[i], node, NULL, NULL);
 	}
 	return arch_early_irq_init();
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c03f71d5ec10..e3e245a4fd70 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1248,6 +1248,31 @@ static void irq_wake_secondary(struct irq_desc *desc, =
struct irqaction *action)
 	raw_spin_unlock_irq(&desc->lock);
 }
=20
+/*
+ * Internal function to notify that a interrupt thread is ready.
+ */
+static void irq_thread_set_ready(struct irq_desc *desc,
+				 struct irqaction *action)
+{
+	set_bit(IRQTF_READY, &action->thread_flags);
+	wake_up(&desc->wait_for_threads);
+}
+
+/*
+ * Internal function to wake up a interrupt thread and wait until it is
+ * ready.
+ */
+static void wake_up_and_wait_for_irq_thread_ready(struct irq_desc *desc,
+						  struct irqaction *action)
+{
+	if (!action || !action->thread)
+		return;
+
+	wake_up_process(action->thread);
+	wait_event(desc->wait_for_threads,
+		   test_bit(IRQTF_READY, &action->thread_flags));
+}
+
 /*
  * Interrupt handler thread
  */
@@ -1259,6 +1284,8 @@ static int irq_thread(void *data)
 	irqreturn_t (*handler_fn)(struct irq_desc *desc,
 			struct irqaction *action);
=20
+	irq_thread_set_ready(desc, action);
+
 	sched_set_fifo(current);
=20
 	if (force_irqthreads() && test_bit(IRQTF_FORCED_THREAD,
@@ -1683,8 +1710,6 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, st=
ruct irqaction *new)
 	}
=20
 	if (!shared) {
-		init_waitqueue_head(&desc->wait_for_threads);
-
 		/* Setup the type (level, edge polarity) if configured: */
 		if (new->flags & IRQF_TRIGGER_MASK) {
 			ret =3D __irq_set_trigger(desc,
@@ -1780,14 +1805,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, s=
truct irqaction *new)
=20
 	irq_setup_timings(desc, new);
=20
-	/*
-	 * Strictly no need to wake it up, but hung_task complains
-	 * when no hard interrupt wakes the thread up.
-	 */
-	if (new->thread)
-		wake_up_process(new->thread);
-	if (new->secondary)
-		wake_up_process(new->secondary->thread);
+	wake_up_and_wait_for_irq_thread_ready(desc, new);
+	wake_up_and_wait_for_irq_thread_ready(desc, new->secondary);
=20
 	register_irq_proc(irq, desc);
 	new->dir =3D NULL;