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linux/kernel/irq/internals.h
Thomas Pfaff 8707898e22 genirq: Synchronize interrupt thread startup 
A kernel hang can be observed when running setserial in a loop on a kernel
with force threaded interrupts. The sequence of events is:

   setserial
     open("/dev/ttyXXX")
       request_irq()
     do_stuff()
      -> serial interrupt
         -> wake(irq_thread)
	      desc->threads_active++;
     close()
       free_irq()
         kthread_stop(irq_thread)
     synchronize_irq() <- hangs because desc->threads_active != 0

The thread is created in request_irq() and woken up, but does not get on a
CPU to reach the actual thread function, which would handle the pending
wake-up. kthread_stop() sets the should stop condition which makes the
thread immediately exit, which in turn leaves the stale threads_active
count around.

This problem was introduced with commit 519cc8652b, which addressed a
interrupt sharing issue in the PCIe code.

Before that commit free_irq() invoked synchronize_irq(), which waits for
the hard interrupt handler and also for associated threads to complete.

To address the PCIe issue synchronize_irq() was replaced with
__synchronize_hardirq(), which only waits for the hard interrupt handler to
complete, but not for threaded handlers.

This was done under the assumption, that the interrupt thread already
reached the thread function and waits for a wake-up, which is guaranteed to
be handled before acting on the stop condition. The problematic case, that
the thread would not reach the thread function, was obviously overlooked.

Make sure that the interrupt thread is really started and reaches
thread_fn() before returning from __setup_irq().

This utilizes the existing wait queue in the interrupt descriptor. The
wait queue is unused for non-shared interrupts. For shared interrupts the
usage might cause a spurious wake-up of a waiter in synchronize_irq() or the
completion of a threaded handler might cause a spurious wake-up of the
waiter for the ready flag. Both are harmless and have no functional impact.

[ tglx: Amended changelog ]

Fixes: 519cc8652b ("genirq: Synchronize only with single thread on free_irq()")
Signed-off-by: Thomas Pfaff <tpfaff@pcs.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/552fe7b4-9224-b183-bb87-a8f36d335690@pcs.com
2022-05-05 11:54:05 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* IRQ subsystem internal functions and variables:
*
* Do not ever include this file from anything else than
* kernel/irq/. Do not even think about using any information outside
* of this file for your non core code.
*/
#include <linux/irqdesc.h>
#include <linux/kernel_stat.h>
#include <linux/pm_runtime.h>
#include <linux/sched/clock.h>
#ifdef CONFIG_SPARSE_IRQ
# define IRQ_BITMAP_BITS (NR_IRQS + 8196)
#else
# define IRQ_BITMAP_BITS NR_IRQS
#endif
#define istate core_internal_state__do_not_mess_with_it
extern bool noirqdebug;
extern struct irqaction chained_action;
/*
* Bits used by threaded handlers:
* IRQTF_RUNTHREAD - signals that the interrupt handler thread should run
* IRQTF_WARNED - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed
* IRQTF_AFFINITY - irq thread is requested to adjust affinity
* IRQTF_FORCED_THREAD - irq action is force threaded
* IRQTF_READY - signals that irq thread is ready
*/
enum {
IRQTF_RUNTHREAD,
IRQTF_WARNED,
IRQTF_AFFINITY,
IRQTF_FORCED_THREAD,
IRQTF_READY,
};
/*
* Bit masks for desc->core_internal_state__do_not_mess_with_it
*
* IRQS_AUTODETECT - autodetection in progress
* IRQS_SPURIOUS_DISABLED - was disabled due to spurious interrupt
* detection
* IRQS_POLL_INPROGRESS - polling in progress
* IRQS_ONESHOT - irq is not unmasked in primary handler
* IRQS_REPLAY - irq is replayed
* IRQS_WAITING - irq is waiting
* IRQS_PENDING - irq is pending and replayed later
* IRQS_SUSPENDED - irq is suspended
* IRQS_NMI - irq line is used to deliver NMIs
*/
enum {
IRQS_AUTODETECT = 0x00000001,
IRQS_SPURIOUS_DISABLED = 0x00000002,
IRQS_POLL_INPROGRESS = 0x00000008,
IRQS_ONESHOT = 0x00000020,
IRQS_REPLAY = 0x00000040,
IRQS_WAITING = 0x00000080,
IRQS_PENDING = 0x00000200,
IRQS_SUSPENDED = 0x00000800,
IRQS_TIMINGS = 0x00001000,
IRQS_NMI = 0x00002000,
};
#include "debug.h"
#include "settings.h"
extern int __irq_set_trigger(struct irq_desc *desc, unsigned long flags);
extern void __disable_irq(struct irq_desc *desc);
extern void __enable_irq(struct irq_desc *desc);
#define IRQ_RESEND true
#define IRQ_NORESEND false
#define IRQ_START_FORCE true
#define IRQ_START_COND false
extern int irq_activate(struct irq_desc *desc);
extern int irq_activate_and_startup(struct irq_desc *desc, bool resend);
extern int irq_startup(struct irq_desc *desc, bool resend, bool force);
extern void irq_shutdown(struct irq_desc *desc);
extern void irq_shutdown_and_deactivate(struct irq_desc *desc);
extern void irq_enable(struct irq_desc *desc);
extern void irq_disable(struct irq_desc *desc);
extern void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu);
extern void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu);
extern void mask_irq(struct irq_desc *desc);
extern void unmask_irq(struct irq_desc *desc);
extern void unmask_threaded_irq(struct irq_desc *desc);
#ifdef CONFIG_SPARSE_IRQ
static inline void irq_mark_irq(unsigned int irq) { }
#else
extern void irq_mark_irq(unsigned int irq);
#endif
extern int __irq_get_irqchip_state(struct irq_data *data,
enum irqchip_irq_state which,
bool *state);
extern void init_kstat_irqs(struct irq_desc *desc, int node, int nr);
irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc);
irqreturn_t handle_irq_event_percpu(struct irq_desc *desc);
irqreturn_t handle_irq_event(struct irq_desc *desc);
/* Resending of interrupts :*/
int check_irq_resend(struct irq_desc *desc, bool inject);
bool irq_wait_for_poll(struct irq_desc *desc);
void __irq_wake_thread(struct irq_desc *desc, struct irqaction *action);
#ifdef CONFIG_PROC_FS
extern void register_irq_proc(unsigned int irq, struct irq_desc *desc);
extern void unregister_irq_proc(unsigned int irq, struct irq_desc *desc);
extern void register_handler_proc(unsigned int irq, struct irqaction *action);
extern void unregister_handler_proc(unsigned int irq, struct irqaction *action);
#else
static inline void register_irq_proc(unsigned int irq, struct irq_desc *desc) { }
static inline void unregister_irq_proc(unsigned int irq, struct irq_desc *desc) { }
static inline void register_handler_proc(unsigned int irq,
struct irqaction *action) { }
static inline void unregister_handler_proc(unsigned int irq,
struct irqaction *action) { }
#endif
extern bool irq_can_set_affinity_usr(unsigned int irq);
extern void irq_set_thread_affinity(struct irq_desc *desc);
extern int irq_do_set_affinity(struct irq_data *data,
const struct cpumask *dest, bool force);
#ifdef CONFIG_SMP
extern int irq_setup_affinity(struct irq_desc *desc);
#else
static inline int irq_setup_affinity(struct irq_desc *desc) { return 0; }
#endif
/* Inline functions for support of irq chips on slow busses */
static inline void chip_bus_lock(struct irq_desc *desc)
{
if (unlikely(desc->irq_data.chip->irq_bus_lock))
desc->irq_data.chip->irq_bus_lock(&desc->irq_data);
}
static inline void chip_bus_sync_unlock(struct irq_desc *desc)
{
if (unlikely(desc->irq_data.chip->irq_bus_sync_unlock))
desc->irq_data.chip->irq_bus_sync_unlock(&desc->irq_data);
}
#define _IRQ_DESC_CHECK (1 << 0)
#define _IRQ_DESC_PERCPU (1 << 1)
#define IRQ_GET_DESC_CHECK_GLOBAL (_IRQ_DESC_CHECK)
#define IRQ_GET_DESC_CHECK_PERCPU (_IRQ_DESC_CHECK | _IRQ_DESC_PERCPU)
#define for_each_action_of_desc(desc, act) \
for (act = desc->action; act; act = act->next)
struct irq_desc *
__irq_get_desc_lock(unsigned int irq, unsigned long *flags, bool bus,
unsigned int check);
void __irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags, bool bus);
static inline struct irq_desc *
irq_get_desc_buslock(unsigned int irq, unsigned long *flags, unsigned int check)
{
return __irq_get_desc_lock(irq, flags, true, check);
}
static inline void
irq_put_desc_busunlock(struct irq_desc *desc, unsigned long flags)
{
__irq_put_desc_unlock(desc, flags, true);
}
static inline struct irq_desc *
irq_get_desc_lock(unsigned int irq, unsigned long *flags, unsigned int check)
{
return __irq_get_desc_lock(irq, flags, false, check);
}
static inline void
irq_put_desc_unlock(struct irq_desc *desc, unsigned long flags)
{
__irq_put_desc_unlock(desc, flags, false);
}
#define __irqd_to_state(d) ACCESS_PRIVATE((d)->common, state_use_accessors)
static inline unsigned int irqd_get(struct irq_data *d)
{
return __irqd_to_state(d);
}
/*
* Manipulation functions for irq_data.state
*/
static inline void irqd_set_move_pending(struct irq_data *d)
{
__irqd_to_state(d) |= IRQD_SETAFFINITY_PENDING;
}
static inline void irqd_clr_move_pending(struct irq_data *d)
{
__irqd_to_state(d) &= ~IRQD_SETAFFINITY_PENDING;
}
static inline void irqd_set_managed_shutdown(struct irq_data *d)
{
__irqd_to_state(d) |= IRQD_MANAGED_SHUTDOWN;
}
static inline void irqd_clr_managed_shutdown(struct irq_data *d)
{
__irqd_to_state(d) &= ~IRQD_MANAGED_SHUTDOWN;
}
static inline void irqd_clear(struct irq_data *d, unsigned int mask)
{
__irqd_to_state(d) &= ~mask;
}
static inline void irqd_set(struct irq_data *d, unsigned int mask)
{
__irqd_to_state(d) |= mask;
}
static inline bool irqd_has_set(struct irq_data *d, unsigned int mask)
{
return __irqd_to_state(d) & mask;
}
static inline void irq_state_set_disabled(struct irq_desc *desc)
{
irqd_set(&desc->irq_data, IRQD_IRQ_DISABLED);
}
static inline void irq_state_set_masked(struct irq_desc *desc)
{
irqd_set(&desc->irq_data, IRQD_IRQ_MASKED);
}
#undef __irqd_to_state
static inline void __kstat_incr_irqs_this_cpu(struct irq_desc *desc)
{
__this_cpu_inc(*desc->kstat_irqs);
__this_cpu_inc(kstat.irqs_sum);
}
static inline void kstat_incr_irqs_this_cpu(struct irq_desc *desc)
{
__kstat_incr_irqs_this_cpu(desc);
desc->tot_count++;
}
static inline int irq_desc_get_node(struct irq_desc *desc)
{
return irq_common_data_get_node(&desc->irq_common_data);
}
static inline int irq_desc_is_chained(struct irq_desc *desc)
{
return (desc->action && desc->action == &chained_action);
}
#ifdef CONFIG_PM_SLEEP
bool irq_pm_check_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_install_action(struct irq_desc *desc, struct irqaction *action) { }
static inline void
irq_pm_remove_action(struct irq_desc *desc, struct irqaction *action) { }
#endif
#ifdef CONFIG_IRQ_TIMINGS
#define IRQ_TIMINGS_SHIFT 5
#define IRQ_TIMINGS_SIZE (1 << IRQ_TIMINGS_SHIFT)
#define IRQ_TIMINGS_MASK (IRQ_TIMINGS_SIZE - 1)
/**
* struct irq_timings - irq timings storing structure
* @values: a circular buffer of u64 encoded <timestamp,irq> values
* @count: the number of elements in the array
*/
struct irq_timings {
u64 values[IRQ_TIMINGS_SIZE];
int count;
};
DECLARE_PER_CPU(struct irq_timings, irq_timings);
extern void irq_timings_free(int irq);
extern int irq_timings_alloc(int irq);
static inline void irq_remove_timings(struct irq_desc *desc)
{
desc->istate &= ~IRQS_TIMINGS;
irq_timings_free(irq_desc_get_irq(desc));
}
static inline void irq_setup_timings(struct irq_desc *desc, struct irqaction *act)
{
int irq = irq_desc_get_irq(desc);
int ret;
/*
* We don't need the measurement because the idle code already
* knows the next expiry event.
*/
if (act->flags & __IRQF_TIMER)
return;
/*
* In case the timing allocation fails, we just want to warn,
* not fail, so letting the system boot anyway.
*/
ret = irq_timings_alloc(irq);
if (ret) {
pr_warn("Failed to allocate irq timing stats for irq%d (%d)",
irq, ret);
return;
}
desc->istate |= IRQS_TIMINGS;
}
extern void irq_timings_enable(void);
extern void irq_timings_disable(void);
DECLARE_STATIC_KEY_FALSE(irq_timing_enabled);
/*
* The interrupt number and the timestamp are encoded into a single
* u64 variable to optimize the size.
* 48 bit time stamp and 16 bit IRQ number is way sufficient.
* Who cares an IRQ after 78 hours of idle time?
*/
static inline u64 irq_timing_encode(u64 timestamp, int irq)
{
return (timestamp << 16) | irq;
}
static inline int irq_timing_decode(u64 value, u64 *timestamp)
{
*timestamp = value >> 16;
return value & U16_MAX;
}
static __always_inline void irq_timings_push(u64 ts, int irq)
{
struct irq_timings *timings = this_cpu_ptr(&irq_timings);
timings->values[timings->count & IRQ_TIMINGS_MASK] =
irq_timing_encode(ts, irq);
timings->count++;
}
/*
* The function record_irq_time is only called in one place in the
* interrupts handler. We want this function always inline so the code
* inside is embedded in the function and the static key branching
* code can act at the higher level. Without the explicit
* __always_inline we can end up with a function call and a small
* overhead in the hotpath for nothing.
*/
static __always_inline void record_irq_time(struct irq_desc *desc)
{
if (!static_branch_likely(&irq_timing_enabled))
return;
if (desc->istate & IRQS_TIMINGS)
irq_timings_push(local_clock(), irq_desc_get_irq(desc));
}
#else
static inline void irq_remove_timings(struct irq_desc *desc) {}
static inline void irq_setup_timings(struct irq_desc *desc,
struct irqaction *act) {};
static inline void record_irq_time(struct irq_desc *desc) {}
#endif /* CONFIG_IRQ_TIMINGS */
#ifdef CONFIG_GENERIC_IRQ_CHIP
void irq_init_generic_chip(struct irq_chip_generic *gc, const char *name,
int num_ct, unsigned int irq_base,
void __iomem *reg_base, irq_flow_handler_t handler);
#else
static inline void
irq_init_generic_chip(struct irq_chip_generic *gc, const char *name,
int num_ct, unsigned int irq_base,
void __iomem *reg_base, irq_flow_handler_t handler) { }
#endif /* CONFIG_GENERIC_IRQ_CHIP */
#ifdef CONFIG_GENERIC_PENDING_IRQ
static inline bool irq_can_move_pcntxt(struct irq_data *data)
{
return irqd_can_move_in_process_context(data);
}
static inline bool irq_move_pending(struct irq_data *data)
{
return irqd_is_setaffinity_pending(data);
}
static inline void
irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask)
{
cpumask_copy(desc->pending_mask, mask);
}
static inline void
irq_get_pending(struct cpumask *mask, struct irq_desc *desc)
{
cpumask_copy(mask, desc->pending_mask);
}
static inline struct cpumask *irq_desc_get_pending_mask(struct irq_desc *desc)
{
return desc->pending_mask;
}
static inline bool handle_enforce_irqctx(struct irq_data *data)
{
return irqd_is_handle_enforce_irqctx(data);
}
bool irq_fixup_move_pending(struct irq_desc *desc, bool force_clear);
#else /* CONFIG_GENERIC_PENDING_IRQ */
static inline bool irq_can_move_pcntxt(struct irq_data *data)
{
return true;
}
static inline bool irq_move_pending(struct irq_data *data)
{
return false;
}
static inline void
irq_copy_pending(struct irq_desc *desc, const struct cpumask *mask)
{
}
static inline void
irq_get_pending(struct cpumask *mask, struct irq_desc *desc)
{
}
static inline struct cpumask *irq_desc_get_pending_mask(struct irq_desc *desc)
{
return NULL;
}
static inline bool irq_fixup_move_pending(struct irq_desc *desc, bool fclear)
{
return false;
}
static inline bool handle_enforce_irqctx(struct irq_data *data)
{
return false;
}
#endif /* !CONFIG_GENERIC_PENDING_IRQ */
#if !defined(CONFIG_IRQ_DOMAIN) || !defined(CONFIG_IRQ_DOMAIN_HIERARCHY)
static inline int irq_domain_activate_irq(struct irq_data *data, bool reserve)
{
irqd_set_activated(data);
return 0;
}
static inline void irq_domain_deactivate_irq(struct irq_data *data)
{
irqd_clr_activated(data);
}
#endif
static inline struct irq_data *irqd_get_parent_data(struct irq_data *irqd)
{
#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
return irqd->parent_data;
#else
return NULL;
#endif
}
#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
#include <linux/debugfs.h>
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 */
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