From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758069Ab1IHGBf (ORCPT ); Thu, 8 Sep 2011 02:01:35 -0400 Received: from mga11.intel.com ([192.55.52.93]:48915 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758034Ab1IHGBD (ORCPT ); Thu, 8 Sep 2011 02:01:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.68,349,1312182000"; d="scan'208";a="50364547" From: Huang Ying To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Andi Kleen , ying.huang@intel.com, Peter Zijlstra , Mathieu Desnoyers Subject: [PATCH -mm -v2 5/5] irq_work, Use llist in irq_work Date: Thu, 8 Sep 2011 14:00:46 +0800 Message-Id: <1315461646-1379-6-git-send-email-ying.huang@intel.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1315461646-1379-1-git-send-email-ying.huang@intel.com> References: <1315461646-1379-1-git-send-email-ying.huang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: Peter Zijlstra --- include/linux/irq_work.h | 15 ++++--- kernel/irq_work.c | 92 ++++++++++++++++------------------------------- 2 files changed, 42 insertions(+), 65 deletions(-) --- a/include/linux/irq_work.h +++ b/include/linux/irq_work.h @@ -1,20 +1,23 @@ #ifndef _LINUX_IRQ_WORK_H #define _LINUX_IRQ_WORK_H +#include + struct irq_work { - struct irq_work *next; + unsigned long flags; + struct llist_node llnode; void (*func)(struct irq_work *); }; 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; - entry->func = func; + work->flags = 0; + 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_sync(struct irq_work *entry); +void irq_work_sync(struct irq_work *work); #endif /* _LINUX_IRQ_WORK_H */ --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -10,7 +10,6 @@ #include #include #include -#include /* * An entry can be in one of four states: @@ -19,54 +18,34 @@ * 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); +static DEFINE_PER_CPU(struct llist_head, irq_work_list); /* * 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 { - next = entry->next; - if ((unsigned long)next & IRQ_WORK_PENDING) + for (;;) { + flags = work->flags; + if (flags & IRQ_WORK_PENDING) return false; - nflags = next_flags(next, IRQ_WORK_FLAGS); - } while (cmpxchg(&entry->next, next, nflags) != next); + nflags = flags | IRQ_WORK_FLAGS; + if (cmpxchg(&work->flags, flags, nflags) == flags) + break; + cpu_relax(); + } return true; } - void __weak arch_irq_work_raise(void) { /* @@ -77,20 +56,15 @@ void __weak arch_irq_work_raise(void) /* * 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(); - do { - 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); - + empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); /* The list was empty, raise self-interrupt to start processing. */ - if (!irq_work_next(entry)) + if (empty) arch_irq_work_raise(); preempt_enable(); @@ -102,16 +76,16 @@ static void __irq_work_queue(struct irq_ * * 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! */ return false; } - __irq_work_queue(entry); + __irq_work_queue(work); return true; } EXPORT_SYMBOL_GPL(irq_work_queue); @@ -122,34 +96,34 @@ EXPORT_SYMBOL_GPL(irq_work_queue); */ 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; BUG_ON(!in_irq()); BUG_ON(!irqs_disabled()); - list = this_cpu_xchg(irq_work_list, NULL); - - while (list != NULL) { - struct irq_work *entry = list; + llnode = llist_del_all(this_list); + while (llnode != NULL) { + work = llist_entry(llnode, struct irq_work, llnode); - list = irq_work_next(list); + llnode = llnode->next; /* - * Clear the PENDING bit, after this point the @entry + * Clear the PENDING bit, after this point the @work * can be re-used. */ - entry->next = next_flags(NULL, IRQ_WORK_BUSY); - entry->func(entry); + work->flags = IRQ_WORK_BUSY; + work->func(work); /* * Clear the BUSY bit and return to the free state if * no-one else claimed it meanwhile. */ - (void)cmpxchg(&entry->next, - next_flags(NULL, IRQ_WORK_BUSY), - NULL); + (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0); } } EXPORT_SYMBOL_GPL(irq_work_run); @@ -158,11 +132,11 @@ 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) +void irq_work_sync(struct irq_work *work) { WARN_ON_ONCE(irqs_disabled()); - while (irq_work_is_set(entry, IRQ_WORK_BUSY)) + while (work->flags & IRQ_WORK_BUSY) cpu_relax(); } EXPORT_SYMBOL_GPL(irq_work_sync);