mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 12:43:55 +08:00
e360adbe29
Provide a mechanism that allows running code in IRQ context. It is most useful for NMI code that needs to interact with the rest of the system -- like wakeup a task to drain buffers. Perf currently has such a mechanism, so extract that and provide it as a generic feature, independent of perf so that others may also benefit. The IRQ context callback is generated through self-IPIs where possible, or on architectures like powerpc the decrementer (the built-in timer facility) is set to generate an interrupt immediately. Architectures that don't have anything like this get to do with a callback from the timer tick. These architectures can call irq_work_run() at the tail of any IRQ handlers that might enqueue such work (like the perf IRQ handler) to avoid undue latencies in processing the work. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Kyle McMartin <kyle@mcmartin.ca> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [ various fixes ] Signed-off-by: Huang Ying <ying.huang@intel.com> LKML-Reference: <1287036094.7768.291.camel@yhuang-dev> Signed-off-by: Ingo Molnar <mingo@elte.hu>
165 lines
3.7 KiB
C
165 lines
3.7 KiB
C
/*
|
|
* Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
|
|
*
|
|
* Provides a framework for enqueueing and running callbacks from hardirq
|
|
* context. The enqueueing is NMI-safe.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/irq_work.h>
|
|
#include <linux/hardirq.h>
|
|
|
|
/*
|
|
* An entry can be in one of four states:
|
|
*
|
|
* free NULL, 0 -> {claimed} : free to be used
|
|
* claimed NULL, 3 -> {pending} : claimed to be enqueued
|
|
* pending next, 3 -> {busy} : queued, pending callback
|
|
* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
|
|
*
|
|
* We use the lower two bits of the next pointer to keep PENDING and BUSY
|
|
* flags.
|
|
*/
|
|
|
|
#define IRQ_WORK_PENDING 1UL
|
|
#define IRQ_WORK_BUSY 2UL
|
|
#define IRQ_WORK_FLAGS 3UL
|
|
|
|
static inline bool irq_work_is_set(struct irq_work *entry, int flags)
|
|
{
|
|
return (unsigned long)entry->next & flags;
|
|
}
|
|
|
|
static inline struct irq_work *irq_work_next(struct irq_work *entry)
|
|
{
|
|
unsigned long next = (unsigned long)entry->next;
|
|
next &= ~IRQ_WORK_FLAGS;
|
|
return (struct irq_work *)next;
|
|
}
|
|
|
|
static inline struct irq_work *next_flags(struct irq_work *entry, int flags)
|
|
{
|
|
unsigned long next = (unsigned long)entry;
|
|
next |= flags;
|
|
return (struct irq_work *)next;
|
|
}
|
|
|
|
static DEFINE_PER_CPU(struct irq_work *, irq_work_list);
|
|
|
|
/*
|
|
* Claim the entry so that no one else will poke at it.
|
|
*/
|
|
static bool irq_work_claim(struct irq_work *entry)
|
|
{
|
|
struct irq_work *next, *nflags;
|
|
|
|
do {
|
|
next = entry->next;
|
|
if ((unsigned long)next & IRQ_WORK_PENDING)
|
|
return false;
|
|
nflags = next_flags(next, IRQ_WORK_FLAGS);
|
|
} while (cmpxchg(&entry->next, next, nflags) != next);
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
void __weak arch_irq_work_raise(void)
|
|
{
|
|
/*
|
|
* Lame architectures will get the timer tick callback
|
|
*/
|
|
}
|
|
|
|
/*
|
|
* Queue the entry and raise the IPI if needed.
|
|
*/
|
|
static void __irq_work_queue(struct irq_work *entry)
|
|
{
|
|
struct irq_work **head, *next;
|
|
|
|
head = &get_cpu_var(irq_work_list);
|
|
|
|
do {
|
|
next = *head;
|
|
/* Can assign non-atomic because we keep the flags set. */
|
|
entry->next = next_flags(next, IRQ_WORK_FLAGS);
|
|
} while (cmpxchg(head, next, entry) != next);
|
|
|
|
/* The list was empty, raise self-interrupt to start processing. */
|
|
if (!irq_work_next(entry))
|
|
arch_irq_work_raise();
|
|
|
|
put_cpu_var(irq_work_list);
|
|
}
|
|
|
|
/*
|
|
* Enqueue the irq_work @entry, returns true on success, failure when the
|
|
* @entry was already enqueued by someone else.
|
|
*
|
|
* Can be re-enqueued while the callback is still in progress.
|
|
*/
|
|
bool irq_work_queue(struct irq_work *entry)
|
|
{
|
|
if (!irq_work_claim(entry)) {
|
|
/*
|
|
* Already enqueued, can't do!
|
|
*/
|
|
return false;
|
|
}
|
|
|
|
__irq_work_queue(entry);
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(irq_work_queue);
|
|
|
|
/*
|
|
* Run the irq_work entries on this cpu. Requires to be ran from hardirq
|
|
* context with local IRQs disabled.
|
|
*/
|
|
void irq_work_run(void)
|
|
{
|
|
struct irq_work *list, **head;
|
|
|
|
head = &__get_cpu_var(irq_work_list);
|
|
if (*head == NULL)
|
|
return;
|
|
|
|
BUG_ON(!in_irq());
|
|
BUG_ON(!irqs_disabled());
|
|
|
|
list = xchg(head, NULL);
|
|
while (list != NULL) {
|
|
struct irq_work *entry = list;
|
|
|
|
list = irq_work_next(list);
|
|
|
|
/*
|
|
* Clear the PENDING bit, after this point the @entry
|
|
* can be re-used.
|
|
*/
|
|
entry->next = next_flags(NULL, IRQ_WORK_BUSY);
|
|
entry->func(entry);
|
|
/*
|
|
* Clear the BUSY bit and return to the free state if
|
|
* no-one else claimed it meanwhile.
|
|
*/
|
|
cmpxchg(&entry->next, next_flags(NULL, IRQ_WORK_BUSY), NULL);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(irq_work_run);
|
|
|
|
/*
|
|
* Synchronize against the irq_work @entry, ensures the entry is not
|
|
* currently in use.
|
|
*/
|
|
void irq_work_sync(struct irq_work *entry)
|
|
{
|
|
WARN_ON_ONCE(irqs_disabled());
|
|
|
|
while (irq_work_is_set(entry, IRQ_WORK_BUSY))
|
|
cpu_relax();
|
|
}
|
|
EXPORT_SYMBOL_GPL(irq_work_sync);
|