Merge tag 'irq-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

torvalds · torvalds · commit dba3ec9f2ad0 · 2025-07-29T12:55:12.000-07:00
Pull irq updates from Thomas Gleixner:

 - Prevent a interrupt migration related live lock in handle_edge_irq()

   If the interrupt affinity is moved to a new target CPU and the
   interrupt is currently handled on the previous target CPU for edge
   type interrupts the handler might get stuck on the previous target
   for a long time, which causes both involved CPUs to waste cycles and
   eventually run into a soft-lockup situation.

   Solve this by checking whether the interrupt is redirected to a new
   target CPU and if the interrupt is handled on that new target CPU,
   busy wait for completion instead of masking it and sending the
   pending but which would cause the old CPU to re-run the handler and
   in the worst case repeating this excercise for a long time.

   This only works on architectures which use single CPU interrupt
   targets, but that's so far the only ones where this behaviour has
   been observed.

 - Add a kunit test for interrupt disable depth counts

   The nested interrupt disable depth has been an issue in the past
   especially vs. free_irq(), interrupt shutdown and CPU hotplug and
   their interactions. The test exercises the combinations of these
   scenarios and checks for correctness.

* tag 'irq-core-2025-07-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq: Prevent migration live lock in handle_edge_irq()
  genirq: Split up irq_pm_check_wakeup()
  genirq: Move irq_wait_for_poll() to call site
  genirq: Remove pointless local variable
  genirq: Add kunit tests for depth counts
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
@@ -144,6 +144,17 @@ config GENERIC_IRQ_DEBUGFS
 config GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
 	bool
 
+config IRQ_KUNIT_TEST
+	bool "KUnit tests for IRQ management APIs" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	default KUNIT_ALL_TESTS
+	imply SMP
+	help
+	  This option enables KUnit tests for the IRQ subsystem API. These are
+	  only for development and testing, not for regular kernel use cases.
+
+	  If unsure, say N.
+
 endmenu
 
 config GENERIC_IRQ_MULTI_HANDLER
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
@@ -19,3 +19,4 @@ obj-$(CONFIG_GENERIC_IRQ_IPI_MUX) += ipi-mux.o
 obj-$(CONFIG_SMP) += affinity.o
 obj-$(CONFIG_GENERIC_IRQ_DEBUGFS) += debugfs.o
 obj-$(CONFIG_GENERIC_IRQ_MATRIX_ALLOCATOR) += matrix.o
+obj-$(CONFIG_IRQ_KUNIT_TEST) += irq_test.o
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
@@ -457,36 +457,88 @@ void unmask_threaded_irq(struct irq_desc *desc)
 	unmask_irq(desc);
 }
 
-static bool irq_check_poll(struct irq_desc *desc)
-{
-	if (!(desc->istate & IRQS_POLL_INPROGRESS))
-		return false;
-	return irq_wait_for_poll(desc);
+/* Busy wait until INPROGRESS is cleared */
+static bool irq_wait_on_inprogress(struct irq_desc *desc)
+{
+	if (IS_ENABLED(CONFIG_SMP)) {
+		do {
+			raw_spin_unlock(&desc->lock);
+			while (irqd_irq_inprogress(&desc->irq_data))
+				cpu_relax();
+			raw_spin_lock(&desc->lock);
+		} while (irqd_irq_inprogress(&desc->irq_data));
+
+		/* Might have been disabled in meantime */
+		return !irqd_irq_disabled(&desc->irq_data) && desc->action;
+	}
+	return false;
 }
 
 static bool irq_can_handle_pm(struct irq_desc *desc)
 {
-	unsigned int mask = IRQD_IRQ_INPROGRESS | IRQD_WAKEUP_ARMED;
+	struct irq_data *irqd = &desc->irq_data;
+	const struct cpumask *aff;
 
 	/*
 	 * If the interrupt is not in progress and is not an armed
 	 * wakeup interrupt, proceed.
 	 */
-	if (!irqd_has_set(&desc->irq_data, mask))
+	if (!irqd_has_set(irqd, IRQD_IRQ_INPROGRESS | IRQD_WAKEUP_ARMED))
 		return true;
 
 	/*
 	 * If the interrupt is an armed wakeup source, mark it pending
 	 * and suspended, disable it and notify the pm core about the
 	 * event.
 	 */
-	if (irq_pm_check_wakeup(desc))
+	if (unlikely(irqd_has_set(irqd, IRQD_WAKEUP_ARMED))) {
+		irq_pm_handle_wakeup(desc);
+		return false;
+	}
+
+	/* Check whether the interrupt is polled on another CPU */
+	if (unlikely(desc->istate & IRQS_POLL_INPROGRESS)) {
+		if (WARN_ONCE(irq_poll_cpu == smp_processor_id(),
+			      "irq poll in progress on cpu %d for irq %d\n",
+			      smp_processor_id(), desc->irq_data.irq))
+			return false;
+		return irq_wait_on_inprogress(desc);
+	}
+
+	/* The below works only for single target interrupts */
+	if (!IS_ENABLED(CONFIG_GENERIC_IRQ_EFFECTIVE_AFF_MASK) ||
+	    !irqd_is_single_target(irqd) || desc->handle_irq != handle_edge_irq)
 		return false;
 
 	/*
-	 * Handle a potential concurrent poll on a different core.
+	 * If the interrupt affinity was moved to this CPU and the
+	 * interrupt is currently handled on the previous target CPU, then
+	 * busy wait for INPROGRESS to be cleared. Otherwise for edge type
+	 * interrupts the handler might get stuck on the previous target:
+	 *
+	 * CPU 0			CPU 1 (new target)
+	 * handle_edge_irq()
+	 * repeat:
+	 *	handle_event()		handle_edge_irq()
+	 *			        if (INPROGESS) {
+	 *				  set(PENDING);
+	 *				  mask();
+	 *				  return;
+	 *				}
+	 *	if (PENDING) {
+	 *	  clear(PENDING);
+	 *	  unmask();
+	 *	  goto repeat;
+	 *	}
+	 *
+	 * This happens when the device raises interrupts with a high rate
+	 * and always before handle_event() completes and the CPU0 handler
+	 * can clear INPROGRESS. This has been observed in virtual machines.
 	 */
-	return irq_check_poll(desc);
+	aff = irq_data_get_effective_affinity_mask(irqd);
+	if (cpumask_first(aff) != smp_processor_id())
+		return false;
+	return irq_wait_on_inprogress(desc);
 }
 
 static inline bool irq_can_handle_actions(struct irq_desc *desc)
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
@@ -20,6 +20,7 @@
 #define istate core_internal_state__do_not_mess_with_it
 
 extern bool noirqdebug;
+extern int irq_poll_cpu;
 
 extern struct irqaction chained_action;
 
@@ -112,7 +113,6 @@ irqreturn_t handle_irq_event(struct irq_desc *desc);
 int check_irq_resend(struct irq_desc *desc, bool inject);
 void clear_irq_resend(struct irq_desc *desc);
 void irq_resend_init(struct irq_desc *desc);
-bool irq_wait_for_poll(struct irq_desc *desc);
 void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);
 
 void wake_threads_waitq(struct irq_desc *desc);
@@ -277,11 +277,11 @@ static inline bool irq_is_nmi(struct irq_desc *desc)
 }
 
 #ifdef CONFIG_PM_SLEEP
-bool irq_pm_check_wakeup(struct irq_desc *desc);
+void irq_pm_handle_wakeup(struct irq_desc *desc);
 void irq_pm_install_action(struct irq_desc *desc, struct irqaction *action);
 void irq_pm_remove_action(struct irq_desc *desc, struct irqaction *action);
 #else
-static inline bool irq_pm_check_wakeup(struct irq_desc *desc) { return false; }
+static inline void irq_pm_handle_wakeup(struct irq_desc *desc) { }
 static inline void
 irq_pm_install_action(struct irq_desc *desc, struct irqaction *action) { }
 static inline void
diff --git a/kernel/irq/irq_test.c b/kernel/irq/irq_test.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: LGPL-2.1+
+
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+#include <linux/irqdomain.h>
+#include <linux/nodemask.h>
+#include <kunit/test.h>
+
+#include "internals.h"
+
+static irqreturn_t noop_handler(int irq, void *data)
+{
+	return IRQ_HANDLED;
+}
+
+static void noop(struct irq_data *data) { }
+static unsigned int noop_ret(struct irq_data *data) { return 0; }
+
+static int noop_affinity(struct irq_data *data, const struct cpumask *dest,
+			 bool force)
+{
+	irq_data_update_effective_affinity(data, dest);
+
+	return 0;
+}
+
+static struct irq_chip fake_irq_chip = {
+	.name           = "fake",
+	.irq_startup    = noop_ret,
+	.irq_shutdown   = noop,
+	.irq_enable     = noop,
+	.irq_disable    = noop,
+	.irq_ack        = noop,
+	.irq_mask       = noop,
+	.irq_unmask     = noop,
+	.irq_set_affinity = noop_affinity,
+	.flags          = IRQCHIP_SKIP_SET_WAKE,
+};
+
+static void irq_disable_depth_test(struct kunit *test)
+{
+	struct irq_desc *desc;
+	int virq, ret;
+
+	virq = irq_domain_alloc_descs(-1, 1, 0, NUMA_NO_NODE, NULL);
+	KUNIT_ASSERT_GE(test, virq, 0);
+
+	irq_set_chip_and_handler(virq, &dummy_irq_chip, handle_simple_irq);
+
+	desc = irq_to_desc(virq);
+	KUNIT_ASSERT_PTR_NE(test, desc, NULL);
+
+	ret = request_irq(virq, noop_handler, 0, "test_irq", NULL);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	disable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	enable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	free_irq(virq, NULL);
+}
+
+static void irq_free_disabled_test(struct kunit *test)
+{
+	struct irq_desc *desc;
+	int virq, ret;
+
+	virq = irq_domain_alloc_descs(-1, 1, 0, NUMA_NO_NODE, NULL);
+	KUNIT_ASSERT_GE(test, virq, 0);
+
+	irq_set_chip_and_handler(virq, &dummy_irq_chip, handle_simple_irq);
+
+	desc = irq_to_desc(virq);
+	KUNIT_ASSERT_PTR_NE(test, desc, NULL);
+
+	ret = request_irq(virq, noop_handler, 0, "test_irq", NULL);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	disable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	free_irq(virq, NULL);
+	KUNIT_EXPECT_GE(test, desc->depth, 1);
+
+	ret = request_irq(virq, noop_handler, 0, "test_irq", NULL);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	free_irq(virq, NULL);
+}
+
+static void irq_shutdown_depth_test(struct kunit *test)
+{
+	struct irq_desc *desc;
+	struct irq_data *data;
+	int virq, ret;
+	struct irq_affinity_desc affinity = {
+		.is_managed = 1,
+		.mask = CPU_MASK_ALL,
+	};
+
+	if (!IS_ENABLED(CONFIG_SMP))
+		kunit_skip(test, "requires CONFIG_SMP for managed shutdown");
+
+	virq = irq_domain_alloc_descs(-1, 1, 0, NUMA_NO_NODE, &affinity);
+	KUNIT_ASSERT_GE(test, virq, 0);
+
+	irq_set_chip_and_handler(virq, &dummy_irq_chip, handle_simple_irq);
+
+	desc = irq_to_desc(virq);
+	KUNIT_ASSERT_PTR_NE(test, desc, NULL);
+
+	data = irq_desc_get_irq_data(desc);
+	KUNIT_ASSERT_PTR_NE(test, data, NULL);
+
+	ret = request_irq(virq, noop_handler, 0, "test_irq", NULL);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_TRUE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_TRUE(test, irqd_is_started(data));
+	KUNIT_EXPECT_TRUE(test, irqd_affinity_is_managed(data));
+
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	disable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	irq_shutdown_and_deactivate(desc);
+
+	KUNIT_EXPECT_FALSE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_FALSE(test, irqd_is_started(data));
+
+	KUNIT_EXPECT_EQ(test, irq_activate(desc), 0);
+#ifdef CONFIG_SMP
+	irq_startup_managed(desc);
+#endif
+
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	enable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	free_irq(virq, NULL);
+}
+
+static void irq_cpuhotplug_test(struct kunit *test)
+{
+	struct irq_desc *desc;
+	struct irq_data *data;
+	int virq, ret;
+	struct irq_affinity_desc affinity = {
+		.is_managed = 1,
+	};
+
+	if (!IS_ENABLED(CONFIG_SMP))
+		kunit_skip(test, "requires CONFIG_SMP for CPU hotplug");
+	if (!get_cpu_device(1))
+		kunit_skip(test, "requires more than 1 CPU for CPU hotplug");
+	if (!cpu_is_hotpluggable(1))
+		kunit_skip(test, "CPU 1 must be hotpluggable");
+
+	cpumask_copy(&affinity.mask, cpumask_of(1));
+
+	virq = irq_domain_alloc_descs(-1, 1, 0, NUMA_NO_NODE, &affinity);
+	KUNIT_ASSERT_GE(test, virq, 0);
+
+	irq_set_chip_and_handler(virq, &fake_irq_chip, handle_simple_irq);
+
+	desc = irq_to_desc(virq);
+	KUNIT_ASSERT_PTR_NE(test, desc, NULL);
+
+	data = irq_desc_get_irq_data(desc);
+	KUNIT_ASSERT_PTR_NE(test, data, NULL);
+
+	ret = request_irq(virq, noop_handler, 0, "test_irq", NULL);
+	KUNIT_EXPECT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_TRUE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_TRUE(test, irqd_is_started(data));
+	KUNIT_EXPECT_TRUE(test, irqd_affinity_is_managed(data));
+
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	disable_irq(virq);
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	KUNIT_EXPECT_EQ(test, remove_cpu(1), 0);
+	KUNIT_EXPECT_FALSE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_FALSE(test, irqd_is_started(data));
+	KUNIT_EXPECT_GE(test, desc->depth, 1);
+	KUNIT_EXPECT_EQ(test, add_cpu(1), 0);
+
+	KUNIT_EXPECT_FALSE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_FALSE(test, irqd_is_started(data));
+	KUNIT_EXPECT_EQ(test, desc->depth, 1);
+
+	enable_irq(virq);
+	KUNIT_EXPECT_TRUE(test, irqd_is_activated(data));
+	KUNIT_EXPECT_TRUE(test, irqd_is_started(data));
+	KUNIT_EXPECT_EQ(test, desc->depth, 0);
+
+	free_irq(virq, NULL);
+}
+
+static struct kunit_case irq_test_cases[] = {
+	KUNIT_CASE(irq_disable_depth_test),
+	KUNIT_CASE(irq_free_disabled_test),
+	KUNIT_CASE(irq_shutdown_depth_test),
+	KUNIT_CASE(irq_cpuhotplug_test),
+	{}
+};
+
+static struct kunit_suite irq_test_suite = {
+	.name = "irq_test_cases",
+	.test_cases = irq_test_cases,
+};
+
+kunit_test_suite(irq_test_suite);
+MODULE_DESCRIPTION("IRQ unit test suite");
+MODULE_LICENSE("GPL");
diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
