Files
Radu Rendec 57d1220979 genirq: Remove unnecessary NULL check of the kstat_irqs field
The kstat_irqs field of struct irq_desc is used to store a per-cpu count
of interrupt events. It is initialized in init_desc(), along with all
the other fields in struct irq_desc that need explicit initialization,
and therefore it's always available (non-NULL) for any valid interrupt
descriptor (with a caveat - see below).

When CONFIG_SPARSE_IRQ is enabled, all interrupt descriptors are always
allocated dynamically via alloc_desc(), which calls init_desc(), so in
that case kstat_irqs is guaranteed to be non-NULL before a valid struct
irq_desc pointer is even returned.

By contrast, when CONFIG_SPARSE_IRQ is disabled, interrupt descriptors
are allocated statically in the irq_desc[] array, and kstat_irqs is
initialized implicitly to NULL. The per-cpu pointer is initialized only
later, for all descriptors, via start_kernel() -> early_irq_init() ->
init_desc().

The kstat_irqs field is used mostly for printing interrupt statistics
(i.e. reading /proc/interrupts), and that cannot happen until much
later, when user-space is fully initialized. So, there is no concern
with that use case.

The list below includes all functions where the NULL check is removed,
along with a list of all possible call chains and/or a brief explanation
of why it's safe to remove the NULL check in that case.

  * irq_desc_kstat_cpu() [include/linux/irqdesc.h]
    - All direct call sites use it for printing IRQ statistics.

    - Indirect call site: per_cpu_count_show() - also used for printing
      interruptstatistics.

  * kstat_irqs_cpu() [kernel/irq/irqdesc.c]
    - Called by sun3_int7() and sun3_int5() [arch/m68k/sun3/sun3ints.c]
      These are interrupt handlers and cannot be called until their
      corresponding interrupts are initialized in sun3_init_IRQ(). The
      call chain leading to that is:
        start_kernel() -> init_IRQ() [arch/m68k/kernel/ints.c] ->
        mach_init_IRQ = sun3_init_IRQ()
      The init_IRQ() call happens right *after* the early_irq_init() call,
      which means the descriptors are already fully initialized by the
      time the interrupt handlers are even registered.

    - Called by show_interrupts() [arch/s390/kernel/irq.c] - used for
      printing interrupt statistics.

  * kstat_irqs() [kernel/irq/irqdesc.c]
      The only possible call chain is via fs/proc/stat.c:
      stat_open() -> show_stat() -> show_all_irqs() -> kstat_irqs_usr() ->
      kstat_irqs()
      It is used for printing interrupt statistics.

  * kstat_snapshot_irqs()
      The only possible call chain is via kernel/watchdog.c:
        watchdog_timer_fn() -> is_softlockup() -> start_counting_irqs() ->
        kstat_snapshot_irqs()
      The watchdog timer cannot fire early, before early_irq_init().

  * kstat_get_irq_since_snapshot()
      The only possible call chain is via kernel/watchdog.c:
        watchdog_timer_fn() -> report_cpu_status() -> print_irq_counts() ->
        kstat_get_irq_since_snapshot()
      The watchdog timer cannot fire early, before early_irq_init().

Signed-off-by: Radu Rendec <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://patch.msgid.link/[email protected]
2026-07-07 21:36:18 +02:00

283 lines
8.6 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_IRQDESC_H
#define _LINUX_IRQDESC_H
#include <linux/irq_work.h>
#include <linux/kobject.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
/*
* Core internal functions to deal with irq descriptors
*/
struct irq_affinity_notify;
struct proc_dir_entry;
struct module;
struct irq_desc;
struct irq_domain;
struct pt_regs;
/**
* struct irqstat - interrupt statistics
* @cnt: real-time interrupt count
* @ref: snapshot of interrupt count
*/
struct irqstat {
unsigned int cnt;
#ifdef CONFIG_GENERIC_IRQ_STAT_SNAPSHOT
unsigned int ref;
#endif
};
/**
* struct irq_redirect - interrupt redirection metadata
* @work: Harg irq_work item for handler execution on a different CPU
* @target_cpu: CPU to run irq handler on in case the current CPU is not part
* of the irq affinity mask
*/
struct irq_redirect {
struct irq_work work;
unsigned int target_cpu;
};
/**
* struct irq_desc - interrupt descriptor
* @irq_common_data: per irq and chip data passed down to chip functions
* @kstat_irqs: irq stats per cpu
* @handle_irq: highlevel irq-events handler
* @action: the irq action chain
* @status_use_accessors: status information
* @core_internal_state__do_not_mess_with_it: core internal status information
* @depth: disable-depth, for nested irq_disable() calls
* @wake_depth: enable depth, for multiple irq_set_irq_wake() callers
* @tot_count: stats field for non-percpu irqs
* @last_unhandled: aging timer for unhandled count
* @irq_count: stats field to detect stalled irqs
* @irqs_unhandled: stats field for spurious unhandled interrupts
* @threads_handled: stats field for deferred spurious detection of threaded handlers
* @threads_handled_last: comparator field for deferred spurious detection of threaded handlers
* @lock: locking for SMP
* @redirect: Facility for redirecting interrupts via irq_work
* @affinity_hint: hint to user space for preferred irq affinity
* @affinity_notify: context for notification of affinity changes
* @pending_mask: pending rebalanced interrupts
* @threads_oneshot: bitfield to handle shared oneshot threads
* @threads_active: number of irqaction threads currently running
* @wait_for_threads: wait queue for sync_irq to wait for threaded handlers
* @nr_actions: number of installed actions on this descriptor
* @no_suspend_depth: number of irqactions on a irq descriptor with
* IRQF_NO_SUSPEND set
* @force_resume_depth: number of irqactions on a irq descriptor with
* IRQF_FORCE_RESUME set
* @refcnt: Reference count mainly for /proc/interrupts
* @rcu: rcu head for delayed free
* @kobj: kobject used to represent this struct in sysfs
* @request_mutex: mutex to protect request/free before locking desc->lock
* @dir: /proc/irq/ procfs entry
* @debugfs_file: dentry for the debugfs file
* @name: flow handler name for /proc/interrupts output
*/
struct irq_desc {
struct irq_common_data irq_common_data;
struct irq_data irq_data;
struct irqstat __percpu *kstat_irqs;
irq_flow_handler_t handle_irq;
struct irqaction *action; /* IRQ action list */
unsigned int status_use_accessors;
unsigned int core_internal_state__do_not_mess_with_it;
unsigned int depth; /* nested irq disables */
unsigned int wake_depth; /* nested wake enables */
unsigned long tot_count;
unsigned long last_unhandled; /* Aging timer for unhandled count */
unsigned int irq_count; /* For detecting broken IRQs */
unsigned int irqs_unhandled;
atomic_t threads_handled;
int threads_handled_last;
raw_spinlock_t lock;
struct cpumask *percpu_enabled;
#ifdef CONFIG_SMP
struct irq_redirect redirect;
const struct cpumask *affinity_hint;
struct irq_affinity_notify *affinity_notify;
#ifdef CONFIG_GENERIC_PENDING_IRQ
cpumask_var_t pending_mask;
#endif
#endif
unsigned long threads_oneshot;
atomic_t threads_active;
wait_queue_head_t wait_for_threads;
#ifdef CONFIG_PM_SLEEP
unsigned int nr_actions;
unsigned int no_suspend_depth;
unsigned int cond_suspend_depth;
unsigned int force_resume_depth;
#endif
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *dir;
#endif
#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
struct dentry *debugfs_file;
const char *dev_name;
#endif
rcuref_t refcnt;
#ifdef CONFIG_SPARSE_IRQ
struct rcu_head rcu;
struct kobject kobj;
#endif
struct mutex request_mutex;
int parent_irq;
struct module *owner;
const char *name;
#ifdef CONFIG_HARDIRQS_SW_RESEND
struct hlist_node resend_node;
#endif
} ____cacheline_internodealigned_in_smp;
#ifdef CONFIG_SPARSE_IRQ
extern void irq_lock_sparse(void);
extern void irq_unlock_sparse(void);
#else
static inline void irq_lock_sparse(void) { }
static inline void irq_unlock_sparse(void) { }
extern struct irq_desc irq_desc[NR_IRQS];
#endif
static inline unsigned int irq_desc_kstat_cpu(struct irq_desc *desc,
unsigned int cpu)
{
return per_cpu(desc->kstat_irqs->cnt, cpu);
}
static inline struct irq_desc *irq_data_to_desc(struct irq_data *data)
{
return container_of(data->common, struct irq_desc, irq_common_data);
}
static inline unsigned int irq_desc_get_irq(struct irq_desc *desc)
{
return desc->irq_data.irq;
}
static inline struct irq_data *irq_desc_get_irq_data(struct irq_desc *desc)
{
return &desc->irq_data;
}
static inline struct irq_chip *irq_desc_get_chip(struct irq_desc *desc)
{
return desc->irq_data.chip;
}
static inline void *irq_desc_get_chip_data(struct irq_desc *desc)
{
return desc->irq_data.chip_data;
}
static inline void *irq_desc_get_handler_data(struct irq_desc *desc)
{
return desc->irq_common_data.handler_data;
}
/*
* Architectures call this to let the generic IRQ layer
* handle an interrupt.
*/
static inline void generic_handle_irq_desc(struct irq_desc *desc)
{
desc->handle_irq(desc);
}
int handle_irq_desc(struct irq_desc *desc);
int generic_handle_irq(unsigned int irq);
int generic_handle_irq_safe(unsigned int irq);
#ifdef CONFIG_IRQ_DOMAIN
/*
* Convert a HW interrupt number to a logical one using a IRQ domain,
* and handle the result interrupt number. Return -EINVAL if
* conversion failed.
*/
int generic_handle_domain_irq(struct irq_domain *domain, irq_hw_number_t hwirq);
int generic_handle_domain_irq_safe(struct irq_domain *domain, irq_hw_number_t hwirq);
int generic_handle_domain_nmi(struct irq_domain *domain, irq_hw_number_t hwirq);
bool generic_handle_demux_domain_irq(struct irq_domain *domain, irq_hw_number_t hwirq);
#endif
/* Test to see if a driver has successfully requested an irq */
static inline int irq_desc_has_action(struct irq_desc *desc)
{
return desc && desc->action != NULL;
}
/**
* irq_set_handler_locked - Set irq handler from a locked region
* @data: Pointer to the irq_data structure which identifies the irq
* @handler: Flow control handler function for this interrupt
*
* Sets the handler in the irq descriptor associated to @data.
*
* Must be called with irq_desc locked and valid parameters. Typical
* call site is the irq_set_type() callback.
*/
static inline void irq_set_handler_locked(struct irq_data *data,
irq_flow_handler_t handler)
{
struct irq_desc *desc = irq_data_to_desc(data);
desc->handle_irq = handler;
}
/**
* irq_set_chip_handler_name_locked - Set chip, handler and name from a locked region
* @data: Pointer to the irq_data structure for which the chip is set
* @chip: Pointer to the new irq chip
* @handler: Flow control handler function for this interrupt
* @name: Name of the interrupt
*
* Replace the irq chip at the proper hierarchy level in @data and
* sets the handler and name in the associated irq descriptor.
*
* Must be called with irq_desc locked and valid parameters.
*/
static inline void
irq_set_chip_handler_name_locked(struct irq_data *data,
const struct irq_chip *chip,
irq_flow_handler_t handler, const char *name)
{
struct irq_desc *desc = irq_data_to_desc(data);
desc->handle_irq = handler;
desc->name = name;
data->chip = (struct irq_chip *)chip;
}
bool irq_check_status_bit(unsigned int irq, unsigned int bitmask);
static inline bool irq_balancing_disabled(unsigned int irq)
{
return irq_check_status_bit(irq, IRQ_NO_BALANCING_MASK);
}
static inline bool irq_is_percpu(unsigned int irq)
{
return irq_check_status_bit(irq, IRQ_PER_CPU);
}
static inline bool irq_is_percpu_devid(unsigned int irq)
{
return irq_check_status_bit(irq, IRQ_PER_CPU_DEVID);
}
void __irq_set_lockdep_class(unsigned int irq, struct lock_class_key *lock_class,
struct lock_class_key *request_class);
static inline void
irq_set_lockdep_class(unsigned int irq, struct lock_class_key *lock_class,
struct lock_class_key *request_class)
{
if (IS_ENABLED(CONFIG_LOCKDEP))
__irq_set_lockdep_class(irq, lock_class, request_class);
}
#endif