genirq/proc: Runtime size the chip name

The chip name column in the /proc/interrupt output is 8 characters and
right aligned, which causes visual clutter due to the fixed length and the
alignment. Many interrupt chips, e.g. PCI/MSI[X] have way longer names.

Update the length when a chip is assigned to an interrupt and utilize this
information for the output. Align it left so all chip names start at the
begin of the column.

Update the GDB script as well and disentangle the header maze so it
actually works with all .config combinations.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Link: https://patch.msgid.link/20260517194932.085786035@kernel.org

kernel/irq/chip.c

@@ -47,9 +47,11 @@ int irq_set_chip(unsigned int irq, const struct irq_chip *chip)
 		scoped_irqdesc->irq_data.chip = (struct irq_chip *)(chip ?: &no_irq_chip);
 		ret = 0;
 	}
-	/* For !CONFIG_SPARSE_IRQ make the irq show up in allocated_irqs. */
-	if (!ret)
+	if (!ret) {
+		/* For !CONFIG_SPARSE_IRQ make the irq show up in allocated_irqs. */
 		irq_mark_irq(irq);
+		irq_proc_update_chip(chip);
+	}
 	return ret;
 }
 EXPORT_SYMBOL(irq_set_chip);

kernel/irq/debugfs.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KERNEL_IRQ_DEBUGFS_H
+#define _KERNEL_IRQ_DEBUGFS_H
+
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+#include <linux/debugfs.h>
+
+struct irq_bit_descr {
+	unsigned int	mask;
+	char		*name;
+};
+
+#define BIT_MASK_DESCR(m)	{ .mask = m, .name = #m }
+
+void irq_debug_show_bits(struct seq_file *m, int ind, unsigned int state,
+			 const struct irq_bit_descr *sd, int size);
+
+void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc);
+static inline void irq_remove_debugfs_entry(struct irq_desc *desc)
+{
+	debugfs_remove(desc->debugfs_file);
+	kfree(desc->dev_name);
+}
+void irq_debugfs_copy_devname(int irq, struct device *dev);
+# ifdef CONFIG_IRQ_DOMAIN
+void irq_domain_debugfs_init(struct dentry *root);
+# else
+static inline void irq_domain_debugfs_init(struct dentry *root)
+{
+}
+# endif
+#else /* CONFIG_GENERIC_IRQ_DEBUGFS */
+static inline void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *d)
+{
+}
+static inline void irq_remove_debugfs_entry(struct irq_desc *d)
+{
+}
+static inline void irq_debugfs_copy_devname(int irq, struct device *dev)
+{
+}
+#endif /* CONFIG_GENERIC_IRQ_DEBUGFS */
+
+#endif

kernel/irq/internals.h

@@ -12,6 +12,9 @@
 #include <linux/rcuref.h>
 #include <linux/sched/clock.h>
 
+#include "debugfs.h"
+#include "proc.h"
+
 #ifdef CONFIG_SPARSE_IRQ
 # define MAX_SPARSE_IRQS	INT_MAX
 #else
@@ -149,12 +152,6 @@ static inline void unregister_handler_proc(unsigned int irq,
 static inline void irq_proc_update_valid(struct irq_desc *desc) { }
 #endif
 
-#if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
-void irq_proc_calc_prec(void);
-#else
-static inline void irq_proc_calc_prec(void) { }
-#endif
-
 struct irq_desc *irq_find_desc_at_or_after(unsigned int offset);
 
 extern bool irq_can_set_affinity_usr(unsigned int irq);
@@ -398,42 +395,3 @@ static inline struct irq_data *irqd_get_parent_data(struct irq_data *irqd)
 	return NULL;
 #endif
 }
-
-#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
-#include <linux/debugfs.h>
-
-struct irq_bit_descr {
-	unsigned int	mask;
-	char		*name;
-};
-
-#define BIT_MASK_DESCR(m)	{ .mask = m, .name = #m }
-
-void irq_debug_show_bits(struct seq_file *m, int ind, unsigned int state,
-			 const struct irq_bit_descr *sd, int size);
-
-void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc);
-static inline void irq_remove_debugfs_entry(struct irq_desc *desc)
-{
-	debugfs_remove(desc->debugfs_file);
-	kfree(desc->dev_name);
-}
-void irq_debugfs_copy_devname(int irq, struct device *dev);
-# ifdef CONFIG_IRQ_DOMAIN
-void irq_domain_debugfs_init(struct dentry *root);
-# else
-static inline void irq_domain_debugfs_init(struct dentry *root)
-{
-}
-# endif
-#else /* CONFIG_GENERIC_IRQ_DEBUGFS */
-static inline void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *d)
-{
-}
-static inline void irq_remove_debugfs_entry(struct irq_desc *d)
-{
-}
-static inline void irq_debugfs_copy_devname(int irq, struct device *dev)
-{
-}
-#endif /* CONFIG_GENERIC_IRQ_DEBUGFS */

kernel/irq/irqdomain.c

@@ -20,6 +20,8 @@
 #include <linux/smp.h>
 #include <linux/fs.h>
 
+#include "proc.h"
+
 static LIST_HEAD(irq_domain_list);
 static DEFINE_MUTEX(irq_domain_mutex);
 
@@ -1532,6 +1534,7 @@ int irq_domain_set_hwirq_and_chip(struct irq_domain *domain, unsigned int virq,
 	irq_data->chip = (struct irq_chip *)(chip ? chip : &no_irq_chip);
 	irq_data->chip_data = chip_data;
 
+	irq_proc_update_chip(chip);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_domain_set_hwirq_and_chip);
@@ -2081,7 +2084,7 @@ static void irq_domain_free_one_irq(struct irq_domain *domain, unsigned int virq
 #endif	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
 
 #ifdef CONFIG_GENERIC_IRQ_DEBUGFS
-#include "internals.h"
+#include "debugfs.h"
 
 static struct dentry *domain_dir;
 

kernel/irq/proc.c

@@ -457,10 +457,14 @@ int __weak arch_show_interrupts(struct seq_file *p, int prec)
 	return 0;
 }
 
+static DEFINE_RAW_SPINLOCK(irq_proc_constraints_lock);
+
 static struct irq_proc_constraints {
 	unsigned int	num_prec;
+	unsigned int	chip_width;
 } irq_proc_constraints __read_mostly = {
 	.num_prec	= 4,
+	.chip_width	= 8,
 };
 
 #ifndef ACTUAL_NR_IRQS
@@ -473,7 +477,23 @@ void irq_proc_calc_prec(void)
 
 	for (prec = 4, n = 10000; prec < 10 && n <= total_nr_irqs; ++prec)
 		n *= 10;
-	WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+
+	guard(raw_spinlock_irqsave)(&irq_proc_constraints_lock);
+	if (prec > irq_proc_constraints.num_prec)
+		WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+}
+
+void irq_proc_update_chip(const struct irq_chip *chip)
+{
+	unsigned int len = chip && chip->name ? strlen(chip->name) : 0;
+
+	if (!len || len <= READ_ONCE(irq_proc_constraints.chip_width))
+		return;
+
+	/* Can be invoked from interrupt disabled contexts */
+	guard(raw_spinlock_irqsave)(&irq_proc_constraints_lock);
+	if (len > irq_proc_constraints.chip_width)
+		WRITE_ONCE(irq_proc_constraints.chip_width, len);
 }
 
 /* Same as seq_put_decimal_ull_width(p, " ", cnt, 10) */
@@ -515,6 +535,7 @@ void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts)
 
 int show_interrupts(struct seq_file *p, void *v)
 {
+	unsigned int chip_width = READ_ONCE(irq_proc_constraints.chip_width);
 	unsigned int prec = READ_ONCE(irq_proc_constraints.num_prec);
 	int i = *(loff_t *) v, j;
 	struct irqaction *action;
@@ -550,18 +571,20 @@ int show_interrupts(struct seq_file *p, void *v)
 		irq_proc_emit_counts(p, &desc->kstat_irqs->cnt);
 	else
 		irq_proc_emit_zero_counts(p, num_online_cpus());
-	seq_putc(p, ' ');
+
+	/* Enforce a visual gap */
+	seq_write(p, "  ", 2);
 
 	guard(raw_spinlock_irq)(&desc->lock);
 	if (desc->irq_data.chip) {
 		if (desc->irq_data.chip->irq_print_chip)
 			desc->irq_data.chip->irq_print_chip(&desc->irq_data, p);
 		else if (desc->irq_data.chip->name)
-			seq_printf(p, "%8s", desc->irq_data.chip->name);
+			seq_printf(p, "%-*s", chip_width, desc->irq_data.chip->name);
 		else
-			seq_printf(p, "%8s", "-");
+			seq_printf(p, "%-*s", chip_width, "-");
 	} else {
-		seq_printf(p, "%8s", "None");
+		seq_printf(p, "%-*s", chip_width, "None");
 	}
 
 	seq_putc(p, ' ');

kernel/irq/proc.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KERNEL_IRQ_PROC_H
+#define _KERNEL_IRQ_PROC_H
+
+#if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
+void irq_proc_calc_prec(void);
+void irq_proc_update_chip(const struct irq_chip *chip);
+#else
+static inline void irq_proc_calc_prec(void) { }
+static inline void irq_proc_update_chip(const struct irq_chip *chip) { }
+#endif
+
+#endif

scripts/gdb/linux/interrupts.py

@@ -20,7 +20,7 @@ def irq_desc_is_chained(desc):
 def irqd_is_level(desc):
     return desc['irq_data']['common']['state_use_accessors'] & constants.LX_IRQD_LEVEL
 
-def show_irq_desc(prec, irq):
+def show_irq_desc(prec, chip_width, irq):
     text = ""
 
     desc = mapletree.mtree_load(gdb.parse_and_eval("&sparse_irqs"), irq)
@@ -58,7 +58,7 @@ def show_irq_desc(prec, irq):
         else:
             name = "-"
 
-    text += "  %-8s" % (name)
+    text += "  %-*s" % (chip_width, name)
 
     if desc['irq_data']['domain']:
         text += "  %*lu" % (prec, desc['irq_data']['hwirq'])
@@ -171,11 +171,18 @@ class LxInterruptList(gdb.Command):
 
     def invoke(self, arg, from_tty):
         nr_irqs = gdb.parse_and_eval("total_nr_irqs")
-        prec = 4
-        j = 10000
-        while prec < 10 and j <= nr_irqs:
-            prec += 1
-            j *= 10
+        constr = utils.gdb_eval_or_none('irq_proc_constraints')
+
+        if constr:
+            prec = int(constr['num_prec'])
+            chip_width = int(constr['chip_width'])
+        else:
+            prec = 4
+            j = 10000
+            while prec < 10 and j <= nr_irqs:
+                prec += 1
+                j *= 10
+            chip_width = 8
 
         gdb.write("%*s" % (prec + 8, ""))
         for cpu in cpus.each_online_cpu():
@@ -186,7 +193,7 @@ class LxInterruptList(gdb.Command):
             raise gdb.GdbError("Unable to find the sparse IRQ tree, is CONFIG_SPARSE_IRQ enabled?")
 
         for irq in range(nr_irqs):
-            gdb.write(show_irq_desc(prec, irq))
+            gdb.write(show_irq_desc(prec, chip_width, irq))
         gdb.write(arch_show_interrupts(prec))