lx_kit: support multiple pending IRQs

Decoupling the scheduler execution can lead to missed interrupts
because the current implementation only handles one pending
interrupt and requires immediate processing.

This commit introduces a helper object that is used to capture
any occuring interrupts that are then handled consecutively.

Issue #4927.

repos/dde_linux/src/include/lx_emul/irq.h

@@ -31,7 +31,7 @@ int lx_emul_irq_task_function(void * data);
 
 extern void * lx_emul_irq_task_struct;
 
-unsigned int lx_emul_irq_last(void);
+int lx_emul_pending_irq(void);
 
 int lx_emul_irq_init(struct device_node *node, struct device_node *parent);
 

repos/dde_linux/src/include/lx_kit/device.h

@@ -23,6 +23,8 @@
 #include <util/list.h>
 #include <util/xml_node.h>
 
+#include <lx_kit/pending_irq.h>
+
 namespace Lx_kit {
 	using namespace Genode;
 
@@ -63,7 +65,7 @@ class Lx_kit::Device : List<Device>::Element
 			using Index = Platform::Device::Irq::Index;
 
 			Index                  idx;
-			unsigned               number;
+			Pending_irq            number;
 			Io_signal_handler<Irq> handler;
 			bool                   masked  { true  };
 			bool                   occured { false };

repos/dde_linux/src/include/lx_kit/env.h

@@ -22,6 +22,7 @@
 #include <lx_kit/memory.h>
 #include <lx_kit/scheduler.h>
 #include <lx_kit/timeout.h>
+#include <lx_kit/pending_irq.h>
 
 namespace Lx_kit {
 
@@ -50,7 +51,6 @@ struct Lx_kit::Env
 	Scheduler            scheduler       { env.ep() };
 	Device_list          devices         { env.ep(), heap, platform };
 	Lx_kit::Timeout      timeout         { timer, scheduler };
-	unsigned int         last_irq        { 0 };
 
 	Env(Genode::Env & env) : env(env) { }
 };

repos/dde_linux/src/include/lx_kit/pending_irq.h

@@ -0,0 +1,34 @@
+/*
+ * \brief  Lx_kit pending interrupt utility
+ * \author Josef Soentgen
+ * \date   2023-06-22
+ */
+
+/*
+ * Copyright (C) 2022 Genode Labs GmbH
+ *
+ * This file is distributed under the terms of the GNU General Public License
+ * version 2.
+ */
+
+#ifndef _LX_KIT__PENDING_IRQ_H_
+#define _LX_KIT__PENDING_IRQ_H_
+
+#include <util/fifo.h>
+
+namespace Lx_kit {
+
+	using namespace Genode;
+
+	struct Pending_irq;
+}
+
+
+struct Lx_kit::Pending_irq : Genode::Fifo<Lx_kit::Pending_irq>::Element
+{
+	unsigned value;
+
+	Pending_irq(unsigned value) : value (value) { }
+};
+
+#endif /* _LX_KIT__PENDING_IRQ_H_ */

repos/dde_linux/src/include/lx_kit/scheduler.h

@@ -15,8 +15,10 @@
  */
 
 #include <base/entrypoint.h>
+#include <util/fifo.h>
 #include <util/list.h>
 #include <lx_kit/task.h>
+#include <lx_kit/pending_irq.h>
 
 namespace Lx_kit {
 	class Scheduler;
@@ -45,6 +47,8 @@ class Lx_kit::Scheduler
 
 		Signal_handler<Scheduler> _execute_schedule;
 
+		Genode::Fifo<Lx_kit::Pending_irq> _pending_irqs { };
+
 	public:
 
 		Task & current();
@@ -60,7 +64,13 @@ class Lx_kit::Scheduler
 
 		void execute();
 
-		void unblock_irq_handler();
+		void unblock_irq_handler(Pending_irq &);
+		template <typename FN> void pending_irq(FN const &fn)
+		{
+			_pending_irqs.dequeue([&] (Pending_irq const &pirq) {
+				fn(pirq.value); });
+		}
+
 		void unblock_time_handler();
 
 		Task & task(void * t);

repos/dde_linux/src/lib/lx_emul/irq.cc

@@ -39,7 +39,12 @@ extern "C" void lx_emul_irq_eoi(unsigned int irq)
 }
 
 
-extern "C" unsigned int lx_emul_irq_last()
+extern "C" int lx_emul_pending_irq()
 {
-	return Lx_kit::env().last_irq;
+	int pending_irq = -1;
+
+	Lx_kit::env().scheduler.pending_irq([&] (unsigned int irq) {
+		pending_irq = (int)irq; });
+
+	return pending_irq;
 }

repos/dde_linux/src/lib/lx_emul/pci.cc

@@ -60,7 +60,7 @@ lx_emul_pci_for_each_device(void * bus, lx_emul_add_device_callback_t fn)
 	env().devices.for_each([&] (Device & d) {
 		unsigned irq = 0;
 		d.for_each_irq([&] (Device::Irq & i) {
-			if (!irq) irq = i.number; });
+			if (!irq) irq = i.number.value; });
 
 		d.for_pci_config([&] (Device::Pci_config & cfg) {
 			fn(bus, num++, d.name().string(), cfg.vendor_id, cfg.device_id,

repos/dde_linux/src/lib/lx_emul/pin.cc

@@ -30,6 +30,8 @@ namespace {
 
 			Lx_kit::Env &_env;
 
+			Lx_kit::Pending_irq _pending_irq { 0 };
+
 		public:
 
 			struct Number { unsigned value; };
@@ -38,11 +40,9 @@ namespace {
 
 			void trigger_irq(Number number)
 			{
-				/*
-				 * Mirrored from 'Lx_kit::Device::Irq::handle'
-				 */
-				_env.last_irq = number.value;
-				_env.scheduler.unblock_irq_handler();
+				_pending_irq.value = number.value;
+
+				_env.scheduler.unblock_irq_handler(_pending_irq);
 				_env.scheduler.schedule();
 			}
 	};

repos/dde_linux/src/lib/lx_emul/spec/arm/irqchip.c

@@ -171,22 +171,28 @@ int lx_emul_irq_task_function(void * data)
 	for (;;) {
 		lx_emul_task_schedule(true);
 
-		local_irq_save(flags);
-		irq_enter();
+		for (;;) {
+			irq = lx_emul_pending_irq();
+			if (irq == -1)
+				break;
 
-		irq = dde_irq_domain ? irq_find_mapping(dde_irq_domain,
-		                                        lx_emul_irq_last())
-		                     : lx_emul_irq_last();
+			local_irq_save(flags);
+			irq_enter();
 
-		if (!irq) {
-			ack_bad_irq(irq);
-			WARN_ONCE(true, "Unexpected interrupt %d received!\n", lx_emul_irq_last());
-		} else {
-			generic_handle_irq(irq);
+			irq = dde_irq_domain ? irq_find_mapping(dde_irq_domain,
+			                                        irq)
+			                     : irq;
+
+			if (!irq) {
+				ack_bad_irq(irq);
+				WARN_ONCE(true, "Unexpected interrupt %d received!\n", irq);
+			} else {
+				generic_handle_irq(irq);
+			}
+
+			irq_exit();
+			local_irq_restore(flags);
 		}
-
-		irq_exit();
-		local_irq_restore(flags);
 	}
 
 	return 0;

repos/dde_linux/src/lib/lx_emul/spec/x86/irqchip.c

@@ -53,22 +53,27 @@ int lx_emul_irq_task_function(void * data)
 	for (;;) {
 		lx_emul_task_schedule(true);
 
-		local_irq_save(flags);
-		irq_enter();
+		for (;;) {
 
-		irq = lx_emul_irq_last();
+			irq = lx_emul_pending_irq();
+			if (irq == -1)
+				break;
 
-		if (!irq) {
-			ack_bad_irq(irq);
-			WARN_ONCE(true, "Unexpected interrupt %d received!\n",
-			          lx_emul_irq_last());
-		} else {
-			generic_handle_irq(irq);
-			lx_emul_irq_eoi(irq);
+			local_irq_save(flags);
+			irq_enter();
+
+			if (!irq) {
+				ack_bad_irq(irq);
+				WARN_ONCE(true, "Unexpected interrupt %d received!\n",
+				          irq);
+			} else {
+				generic_handle_irq(irq);
+				lx_emul_irq_eoi(irq);
+			}
+
+			irq_exit();
+			local_irq_restore(flags);
 		}
-
-		irq_exit();
-		local_irq_restore(flags);
 	}
 
 	return 0;

repos/dde_linux/src/lib/lx_emul/virt/irq.cc

@@ -25,7 +25,12 @@ extern "C" void lx_emul_irq_mask(unsigned int ) { }
 extern "C" void lx_emul_irq_eoi(unsigned int ) { }
 
 
-extern "C" unsigned int lx_emul_irq_last()
+extern "C" int lx_emul_pending_irq()
 {
-	return Lx_kit::env().last_irq;
+	int pending_irq = -1;
+
+	Lx_kit::env().scheduler.pending_irq([&] (unsigned int irq) {
+		pending_irq = (int)irq; });
+
+	return pending_irq;
 }

repos/dde_linux/src/lib/lx_kit/device.cc

@@ -56,8 +56,7 @@ void Device::Irq::handle()
 	if (masked)
 		return;
 
-	env().last_irq = number;
-	env().scheduler.unblock_irq_handler();
+	env().scheduler.unblock_irq_handler(number);
 }
 
 
@@ -65,7 +64,8 @@ Device::Irq::Irq(Entrypoint & ep, unsigned idx, unsigned number)
 :
 	idx{idx},
 	number(number),
-	handler(ep, *this, &Irq::_handle) { }
+	handler(ep, *this, &Irq::_handle)
+{ }
 
 
 /************
@@ -144,7 +144,7 @@ bool Device::irq_unmask(unsigned number)
 	bool ret = false;
 
 	for_each_irq([&] (Irq & irq) {
-		if (irq.number != number)
+		if (irq.number.value != number)
 			return;
 
 		ret = true;
@@ -170,7 +170,7 @@ void Device::irq_mask(unsigned number)
 		return;
 
 	for_each_irq([&] (Irq & irq) {
-		if (irq.number == number) irq.masked = true; });
+		if (irq.number.value == number) irq.masked = true; });
 
 }
 
@@ -181,7 +181,7 @@ void Device::irq_ack(unsigned number)
 		return;
 
 	for_each_irq([&] (Irq & irq) {
-		if (irq.number != number || !irq.occured || !irq.session.constructed())
+		if (irq.number.value != number || !irq.occured || !irq.session.constructed())
 			return;
 		irq.occured = false;
 		irq.session->ack();

repos/dde_linux/src/lib/lx_kit/scheduler.cc

@@ -74,8 +74,10 @@ void Scheduler::remove(Task & task)
 }
 
 
-void Scheduler::unblock_irq_handler()
+void Scheduler::unblock_irq_handler(Pending_irq &pirq)
 {
+	_pending_irqs.enqueue(pirq);
+
 	for (Task * t = _present_list.first(); t; t = t->next()) {
 		if (t->type() == Task::IRQ_HANDLER) t->unblock();
 	}