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irq_work: Use llist in the struct irq_work logic 

Use llist in irq_work instead of the lock-less linked list
implementation in irq_work to avoid the code duplication.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1315461646-1379-6-git-send-email-ying.huang@intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Huang Ying 2011-09-08 14:00:46 +08:00 committed by Ingo Molnar
parent 781f7fd916
commit 38aaf8090d
2 changed files with 42 additions and 64 deletions
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15
include/linux/irq_work.h
View File

@ -1,20 +1,23 @@
#ifndef _LINUX_IRQ_WORK_H #ifndef _LINUX_IRQ_WORK_H
#define _LINUX_IRQ_WORK_H #define _LINUX_IRQ_WORK_H
#include <linux/llist.h>
struct irq_work { struct irq_work {
struct irq_work *next; unsigned long flags;
struct llist_node llnode;
void (*func)(struct irq_work *); void (*func)(struct irq_work *);
}; };
static inline static inline
void init_irq_work(struct irq_work *entry, void (*func)(struct irq_work *)) void init_irq_work(struct irq_work *work, void (*func)(struct irq_work *))
{ {
entry->next = NULL; work->flags = 0;
entry->func = func; work->func = func;
} }
bool irq_work_queue(struct irq_work *entry); bool irq_work_queue(struct irq_work *work);
void irq_work_run(void); void irq_work_run(void);
void irq_work_sync(struct irq_work *entry); void irq_work_sync(struct irq_work *work);
#endif /* _LINUX_IRQ_WORK_H */ #endif /* _LINUX_IRQ_WORK_H */

91
kernel/irq_work.c
View File

@ -17,54 +17,34 @@
* claimed NULL, 3 -> {pending} : claimed to be enqueued * claimed NULL, 3 -> {pending} : claimed to be enqueued
* pending next, 3 -> {busy} : queued, pending callback * pending next, 3 -> {busy} : queued, pending callback
* busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed * 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_PENDING 1UL
#define IRQ_WORK_BUSY 2UL #define IRQ_WORK_BUSY 2UL
#define IRQ_WORK_FLAGS 3UL #define IRQ_WORK_FLAGS 3UL
static inline bool irq_work_is_set(struct irq_work *entry, int flags) static DEFINE_PER_CPU(struct llist_head, irq_work_list);
{
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. * Claim the entry so that no one else will poke at it.
*/ */
static bool irq_work_claim(struct irq_work *entry) static bool irq_work_claim(struct irq_work *work)
{ {
struct irq_work *next, *nflags; unsigned long flags, nflags;
do { for (;;) {
next = entry->next; flags = work->flags;
if ((unsigned long)next & IRQ_WORK_PENDING) if (flags & IRQ_WORK_PENDING)
return false; return false;
nflags = next_flags(next, IRQ_WORK_FLAGS); nflags = flags | IRQ_WORK_FLAGS;
} while (cmpxchg(&entry->next, next, nflags) != next); if (cmpxchg(&work->flags, flags, nflags) == flags)
break;
cpu_relax();
}
return true; return true;
} }
void __weak arch_irq_work_raise(void) void __weak arch_irq_work_raise(void)
{ {
/* /*
@ -75,20 +55,15 @@ void __weak arch_irq_work_raise(void)
/* /*
* Queue the entry and raise the IPI if needed. * Queue the entry and raise the IPI if needed.
*/ */
static void __irq_work_queue(struct irq_work *entry) static void __irq_work_queue(struct irq_work *work)
{ {
struct irq_work *next; bool empty;
preempt_disable(); preempt_disable();
do { empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
next = __this_cpu_read(irq_work_list);
/* Can assign non-atomic because we keep the flags set. */
entry->next = next_flags(next, IRQ_WORK_FLAGS);
} while (this_cpu_cmpxchg(irq_work_list, next, entry) != next);
/* The list was empty, raise self-interrupt to start processing. */ /* The list was empty, raise self-interrupt to start processing. */
if (!irq_work_next(entry)) if (empty)
arch_irq_work_raise(); arch_irq_work_raise();
preempt_enable(); preempt_enable();
@ -100,16 +75,16 @@ static void __irq_work_queue(struct irq_work *entry)
* *
* Can be re-enqueued while the callback is still in progress. * Can be re-enqueued while the callback is still in progress.
*/ */
bool irq_work_queue(struct irq_work *entry) bool irq_work_queue(struct irq_work *work)
{ {
if (!irq_work_claim(entry)) { if (!irq_work_claim(work)) {
/* /*
* Already enqueued, can't do! * Already enqueued, can't do!
*/ */
return false; return false;
} }
__irq_work_queue(entry); __irq_work_queue(work);
return true; return true;
} }
EXPORT_SYMBOL_GPL(irq_work_queue); EXPORT_SYMBOL_GPL(irq_work_queue);
@ -120,34 +95,34 @@ EXPORT_SYMBOL_GPL(irq_work_queue);
*/ */
void irq_work_run(void) void irq_work_run(void)
{ {
struct irq_work *list; struct irq_work *work;
struct llist_head *this_list;
struct llist_node *llnode;
if (this_cpu_read(irq_work_list) == NULL) this_list = &__get_cpu_var(irq_work_list);
if (llist_empty(this_list))
return; return;
BUG_ON(!in_irq()); BUG_ON(!in_irq());
BUG_ON(!irqs_disabled()); BUG_ON(!irqs_disabled());
list = this_cpu_xchg(irq_work_list, NULL); llnode = llist_del_all(this_list);
while (llnode != NULL) {
work = llist_entry(llnode, struct irq_work, llnode);
while (list != NULL) { llnode = llnode->next;
struct irq_work *entry = list;
list = irq_work_next(list);
/* /*
* Clear the PENDING bit, after this point the @entry * Clear the PENDING bit, after this point the @work
* can be re-used. * can be re-used.
*/ */
entry->next = next_flags(NULL, IRQ_WORK_BUSY); work->flags = IRQ_WORK_BUSY;
entry->func(entry); work->func(work);
/* /*
* Clear the BUSY bit and return to the free state if * Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile. * no-one else claimed it meanwhile.
*/ */
(void)cmpxchg(&entry->next, (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
next_flags(NULL, IRQ_WORK_BUSY),
NULL);
} }
} }
EXPORT_SYMBOL_GPL(irq_work_run); EXPORT_SYMBOL_GPL(irq_work_run);
@ -156,11 +131,11 @@ EXPORT_SYMBOL_GPL(irq_work_run);
* Synchronize against the irq_work @entry, ensures the entry is not * Synchronize against the irq_work @entry, ensures the entry is not
* currently in use. * currently in use.
*/ */
void irq_work_sync(struct irq_work *entry) void irq_work_sync(struct irq_work *work)
{ {
WARN_ON_ONCE(irqs_disabled()); WARN_ON_ONCE(irqs_disabled());
while (irq_work_is_set(entry, IRQ_WORK_BUSY)) while (work->flags & IRQ_WORK_BUSY)
cpu_relax(); cpu_relax();
} }
EXPORT_SYMBOL_GPL(irq_work_sync); EXPORT_SYMBOL_GPL(irq_work_sync);