genirq: Calculate precision only when required

Calculating the precision of the interrupt number column on every initial
show_interrupt() invocation is a pointless exercise as the underlying
maximum number of interrupts rarely changes.

Calculate it only when that number is modified and let show_interrupts()
use the cached value.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Reviewed-by: Radu Rendec <radu@rendec.net>
Link: https://patch.msgid.link/20260517194931.760664517@kernel.org

diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index e5f3d310a825087e14b9ee73a76e8f9366a91065..be702dd64422bb17d12dc3a362472edbd35ee9c3 100644 (file)
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -134,6 +134,12 @@ 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
+
 extern bool irq_can_set_affinity_usr(unsigned int irq);
 
 extern int irq_do_set_affinity(struct irq_data *data,

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index a7ce1e8165a623490e1b2c0acc6e16a846f21567..90595eefb4779bbe886914fd60ee71db61b0ef44 100644 (file)
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -157,13 +157,12 @@ EXPORT_SYMBOL_GPL(irq_get_nr_irqs);
  *
  * Return: @nr.
  */
-unsigned int irq_set_nr_irqs(unsigned int nr)
+unsigned int __init irq_set_nr_irqs(unsigned int nr)
 {
        total_nr_irqs = nr;
-
+       irq_proc_calc_prec();
        return nr;
 }
-EXPORT_SYMBOL_GPL(irq_set_nr_irqs);
 
 static DEFINE_MUTEX(sparse_irq_lock);
 static struct maple_tree sparse_irqs = MTREE_INIT_EXT(sparse_irqs,
@@ -544,6 +543,7 @@ static bool irq_expand_nr_irqs(unsigned int nr)
        if (nr > MAX_SPARSE_IRQS)
                return false;
        total_nr_irqs = nr;
+       irq_proc_calc_prec();
        return true;
 }
 
@@ -572,6 +572,7 @@ int __init early_irq_init(void)
                desc = alloc_desc(i, node, 0, NULL, NULL);
                irq_insert_desc(i, desc);
        }
+       irq_proc_calc_prec();
        return arch_early_irq_init();
 }
 
@@ -592,7 +593,7 @@ int __init early_irq_init(void)
 
        init_irq_default_affinity();
 
-       printk(KERN_INFO "NR_IRQS: %d\n", NR_IRQS);
+       pr_info("NR_IRQS: %d\n", NR_IRQS);
 
        count = ARRAY_SIZE(irq_desc);
 
@@ -602,6 +603,7 @@ int __init early_irq_init(void)
                        goto __free_desc_res;
        }
 
+       irq_proc_calc_prec();
        return arch_early_irq_init();
 
 __free_desc_res:

diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index cc9c7c907dd2af7ebfe7ac37cba749db1438f158..c635fb62c7837e4550541e3882835b4eca978463 100644 (file)
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -457,10 +457,25 @@ int __weak arch_show_interrupts(struct seq_file *p, int prec)
        return 0;
 }
 
+static struct irq_proc_constraints {
+       unsigned int    num_prec;
+} irq_proc_constraints __read_mostly = {
+       .num_prec       = 3,
+};
+
 #ifndef ACTUAL_NR_IRQS
 # define ACTUAL_NR_IRQS total_nr_irqs
 #endif
 
+void irq_proc_calc_prec(void)
+{
+       unsigned int prec, n;
+
+       for (prec = 3, n = 1000; prec < 10 && n <= total_nr_irqs; ++prec)
+               n *= 10;
+       WRITE_ONCE(irq_proc_constraints.num_prec, prec);
+}
+
 /* Same as seq_put_decimal_ull_width(p, " ", cnt, 10) */
 #define ZSTR1 "          0"
 #define ZSTR1_LEN      (sizeof(ZSTR1) - 1)
@@ -500,9 +515,7 @@ void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts)
 
 int show_interrupts(struct seq_file *p, void *v)
 {
-       const unsigned int nr_irqs = total_nr_irqs;
-       static int prec;
-
+       unsigned int prec = READ_ONCE(irq_proc_constraints.num_prec);
        int i = *(loff_t *) v, j;
        struct irqaction *action;
        struct irq_desc *desc;
@@ -515,9 +528,6 @@ int show_interrupts(struct seq_file *p, void *v)
 
        /* print header and calculate the width of the first column */
        if (i == 0) {
-               for (prec = 3, j = 1000; prec < 10 && j <= nr_irqs; ++prec)
-                       j *= 10;
-
                seq_printf(p, "%*s", prec + 8, "");
                for_each_online_cpu(j)
                        seq_printf(p, "CPU%-8d", j);
@@ -553,13 +563,16 @@ int show_interrupts(struct seq_file *p, void *v)
        } else {
                seq_printf(p, "%8s", "None");
        }
+
+       seq_putc(p, ' ');
        if (desc->irq_data.domain)
-               seq_printf(p, " %*lu", prec, desc->irq_data.hwirq);
+               seq_put_decimal_ull_width(p, "", desc->irq_data.hwirq, prec);
        else
                seq_printf(p, " %*s", prec, "");
-#ifdef CONFIG_GENERIC_IRQ_SHOW_LEVEL
-       seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge");
-#endif
+
+       if (IS_ENABLED(CONFIG_GENERIC_IRQ_SHOW_LEVEL))
+               seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge");
+
        if (desc->name)
                seq_printf(p, "-%-8s", desc->name);