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genirq: Expose interrupt information through sysfs
Information about interrupts is exposed via /proc/interrupts, but the format of that file has changed over kernel versions and differs across architectures. It also has varying column numbers depending on hardware. That all makes it hard for tools to parse. To solve this, expose the information through sysfs so each irq attribute is in a separate file in a consistent, machine parsable way. This feature is only available when both CONFIG_SPARSE_IRQ and CONFIG_SYSFS are enabled. Examples: /sys/kernel/irq/18/actions: i801_smbus,ehci_hcd:usb1,uhci_hcd:usb7 /sys/kernel/irq/18/chip_name: IR-IO-APIC /sys/kernel/irq/18/hwirq: 18 /sys/kernel/irq/18/name: fasteoi /sys/kernel/irq/18/per_cpu_count: 0,0 /sys/kernel/irq/18/type: level /sys/kernel/irq/25/actions: ahci0 /sys/kernel/irq/25/chip_name: IR-PCI-MSI /sys/kernel/irq/25/hwirq: 512000 /sys/kernel/irq/25/name: edge /sys/kernel/irq/25/per_cpu_count: 29036,0 /sys/kernel/irq/25/type: edge [ tglx: Moved kobject_del() under sparse_irq_lock, massaged code comments and changelog ] Signed-off-by: Craig Gallek <kraig@google.com> Cc: David Decotigny <decot@google.com> Link: http://lkml.kernel.org/r/1473783291-122873-1-git-send-email-kraigatgoog@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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‎Documentation/ABI/testing/sysfs-kernel-irq

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@@ -0,0 +1,53 @@
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What: /sys/kernel/irq
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: Directory containing information about the system's IRQs.
6+
Specifically, data from the associated struct irq_desc.
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The information here is similar to that in /proc/interrupts
8+
but in a more machine-friendly format. This directory contains
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one subdirectory for each Linux IRQ number.
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What: /sys/kernel/irq/<irq>/actions
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: The IRQ action chain. A comma-separated list of zero or more
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device names associated with this interrupt.
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What: /sys/kernel/irq/<irq>/chip_name
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: Human-readable chip name supplied by the associated device
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driver.
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What: /sys/kernel/irq/<irq>/hwirq
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: When interrupt translation domains are used, this file contains
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the underlying hardware IRQ number used for this Linux IRQ.
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What: /sys/kernel/irq/<irq>/name
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: Human-readable flow handler name as defined by the irq chip
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driver.
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What: /sys/kernel/irq/<irq>/per_cpu_count
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: The number of times the interrupt has fired since boot. This
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is a comma-separated list of counters; one per CPU in CPU id
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order. NOTE: This file consistently shows counters for all
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CPU ids. This differs from the behavior of /proc/interrupts
47+
which only shows counters for online CPUs.
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What: /sys/kernel/irq/<irq>/type
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Date: September 2016
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KernelVersion: 4.9
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Contact: Craig Gallek <kraig@google.com>
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Description: The type of the interrupt. Either the string 'level' or 'edge'.

‎include/linux/irqdesc.h

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Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@
22
#define _LINUX_IRQDESC_H
33

44
#include <linux/rcupdate.h>
5+
#include <linux/kobject.h>
56

67
/*
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* Core internal functions to deal with irq descriptors
@@ -43,6 +44,7 @@ struct pt_regs;
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* @force_resume_depth: number of irqactions on a irq descriptor with
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* IRQF_FORCE_RESUME set
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* @rcu: rcu head for delayed free
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* @kobj: kobject used to represent this struct in sysfs
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* @dir: /proc/irq/ procfs entry
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* @name: flow handler name for /proc/interrupts output
4850
*/
@@ -88,6 +90,7 @@ struct irq_desc {
8890
#endif
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#ifdef CONFIG_SPARSE_IRQ
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struct rcu_head rcu;
93+
struct kobject kobj;
9194
#endif
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int parent_irq;
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struct module *owner;

‎kernel/irq/irqdesc.c

Lines changed: 191 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@
1515
#include <linux/radix-tree.h>
1616
#include <linux/bitmap.h>
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#include <linux/irqdomain.h>
18+
#include <linux/sysfs.h>
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#include "internals.h"
2021

@@ -123,6 +124,181 @@ static DECLARE_BITMAP(allocated_irqs, IRQ_BITMAP_BITS);
123124

124125
#ifdef CONFIG_SPARSE_IRQ
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127+
static void irq_kobj_release(struct kobject *kobj);
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#ifdef CONFIG_SYSFS
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static struct kobject *irq_kobj_base;
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#define IRQ_ATTR_RO(_name) \
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static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
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static ssize_t per_cpu_count_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
137+
{
138+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
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int cpu, irq = desc->irq_data.irq;
140+
ssize_t ret = 0;
141+
char *p = "";
142+
143+
for_each_possible_cpu(cpu) {
144+
unsigned int c = kstat_irqs_cpu(irq, cpu);
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146+
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%u", p, c);
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p = ",";
148+
}
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150+
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
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return ret;
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}
153+
IRQ_ATTR_RO(per_cpu_count);
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static ssize_t chip_name_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
157+
{
158+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
159+
ssize_t ret = 0;
160+
161+
raw_spin_lock_irq(&desc->lock);
162+
if (desc->irq_data.chip && desc->irq_data.chip->name) {
163+
ret = scnprintf(buf, PAGE_SIZE, "%s\n",
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desc->irq_data.chip->name);
165+
}
166+
raw_spin_unlock_irq(&desc->lock);
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168+
return ret;
169+
}
170+
IRQ_ATTR_RO(chip_name);
171+
172+
static ssize_t hwirq_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
174+
{
175+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
176+
ssize_t ret = 0;
177+
178+
raw_spin_lock_irq(&desc->lock);
179+
if (desc->irq_data.domain)
180+
ret = sprintf(buf, "%d\n", (int)desc->irq_data.hwirq);
181+
raw_spin_unlock_irq(&desc->lock);
182+
183+
return ret;
184+
}
185+
IRQ_ATTR_RO(hwirq);
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187+
static ssize_t type_show(struct kobject *kobj,
188+
struct kobj_attribute *attr, char *buf)
189+
{
190+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
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ssize_t ret = 0;
192+
193+
raw_spin_lock_irq(&desc->lock);
194+
ret = sprintf(buf, "%s\n",
195+
irqd_is_level_type(&desc->irq_data) ? "level" : "edge");
196+
raw_spin_unlock_irq(&desc->lock);
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198+
return ret;
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}
201+
IRQ_ATTR_RO(type);
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static ssize_t name_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
205+
{
206+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
207+
ssize_t ret = 0;
208+
209+
raw_spin_lock_irq(&desc->lock);
210+
if (desc->name)
211+
ret = scnprintf(buf, PAGE_SIZE, "%s\n", desc->name);
212+
raw_spin_unlock_irq(&desc->lock);
213+
214+
return ret;
215+
}
216+
IRQ_ATTR_RO(name);
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218+
static ssize_t actions_show(struct kobject *kobj,
219+
struct kobj_attribute *attr, char *buf)
220+
{
221+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
222+
struct irqaction *action;
223+
ssize_t ret = 0;
224+
char *p = "";
225+
226+
raw_spin_lock_irq(&desc->lock);
227+
for (action = desc->action; action != NULL; action = action->next) {
228+
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
229+
p, action->name);
230+
p = ",";
231+
}
232+
raw_spin_unlock_irq(&desc->lock);
233+
234+
if (ret)
235+
ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
236+
237+
return ret;
238+
}
239+
IRQ_ATTR_RO(actions);
240+
241+
static struct attribute *irq_attrs[] = {
242+
&per_cpu_count_attr.attr,
243+
&chip_name_attr.attr,
244+
&hwirq_attr.attr,
245+
&type_attr.attr,
246+
&name_attr.attr,
247+
&actions_attr.attr,
248+
NULL
249+
};
250+
251+
static struct kobj_type irq_kobj_type = {
252+
.release = irq_kobj_release,
253+
.sysfs_ops = &kobj_sysfs_ops,
254+
.default_attrs = irq_attrs,
255+
};
256+
257+
static void irq_sysfs_add(int irq, struct irq_desc *desc)
258+
{
259+
if (irq_kobj_base) {
260+
/*
261+
* Continue even in case of failure as this is nothing
262+
* crucial.
263+
*/
264+
if (kobject_add(&desc->kobj, irq_kobj_base, "%d", irq))
265+
pr_warn("Failed to add kobject for irq %d\n", irq);
266+
}
267+
}
268+
269+
static int __init irq_sysfs_init(void)
270+
{
271+
struct irq_desc *desc;
272+
int irq;
273+
274+
/* Prevent concurrent irq alloc/free */
275+
irq_lock_sparse();
276+
277+
irq_kobj_base = kobject_create_and_add("irq", kernel_kobj);
278+
if (!irq_kobj_base) {
279+
irq_unlock_sparse();
280+
return -ENOMEM;
281+
}
282+
283+
/* Add the already allocated interrupts */
284+
for_each_irq_desc(irq, desc)
285+
irq_sysfs_add(irq, desc);
286+
irq_unlock_sparse();
287+
288+
return 0;
289+
}
290+
postcore_initcall(irq_sysfs_init);
291+
292+
#else /* !CONFIG_SYSFS */
293+
294+
static struct kobj_type irq_kobj_type = {
295+
.release = irq_kobj_release,
296+
};
297+
298+
static void irq_sysfs_add(int irq, struct irq_desc *desc) {}
299+
300+
#endif /* CONFIG_SYSFS */
301+
126302
static RADIX_TREE(irq_desc_tree, GFP_KERNEL);
127303

128304
static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)
@@ -187,6 +363,7 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
187363

188364
desc_set_defaults(irq, desc, node, affinity, owner);
189365
irqd_set(&desc->irq_data, flags);
366+
kobject_init(&desc->kobj, &irq_kobj_type);
190367

191368
return desc;
192369

@@ -197,15 +374,22 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
197374
return NULL;
198375
}
199376

200-
static void delayed_free_desc(struct rcu_head *rhp)
377+
static void irq_kobj_release(struct kobject *kobj)
201378
{
202-
struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
379+
struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
203380

204381
free_masks(desc);
205382
free_percpu(desc->kstat_irqs);
206383
kfree(desc);
207384
}
208385

386+
static void delayed_free_desc(struct rcu_head *rhp)
387+
{
388+
struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
389+
390+
kobject_put(&desc->kobj);
391+
}
392+
209393
static void free_desc(unsigned int irq)
210394
{
211395
struct irq_desc *desc = irq_to_desc(irq);
@@ -217,8 +401,12 @@ static void free_desc(unsigned int irq)
217401
* kstat_irq_usr(). Once we deleted the descriptor from the
218402
* sparse tree we can free it. Access in proc will fail to
219403
* lookup the descriptor.
404+
*
405+
* The sysfs entry must be serialized against a concurrent
406+
* irq_sysfs_init() as well.
220407
*/
221408
mutex_lock(&sparse_irq_lock);
409+
kobject_del(&desc->kobj);
222410
delete_irq_desc(irq);
223411
mutex_unlock(&sparse_irq_lock);
224412

@@ -261,6 +449,7 @@ static int alloc_descs(unsigned int start, unsigned int cnt, int node,
261449
goto err;
262450
mutex_lock(&sparse_irq_lock);
263451
irq_insert_desc(start + i, desc);
452+
irq_sysfs_add(start + i, desc);
264453
mutex_unlock(&sparse_irq_lock);
265454
}
266455
return start;

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