Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
| 3 | * |
| 4 | * Provides a framework for enqueueing and running callbacks from hardirq |
| 5 | * context. The enqueueing is NMI-safe. |
| 6 | */ |
| 7 | |
Paul Gortmaker | 83e3fa6 | 2012-04-01 16:38:37 -0400 | [diff] [blame] | 8 | #include <linux/bug.h> |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 9 | #include <linux/kernel.h> |
Paul Gortmaker | 9984de1 | 2011-05-23 14:51:41 -0400 | [diff] [blame] | 10 | #include <linux/export.h> |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 11 | #include <linux/irq_work.h> |
Paul Gortmaker | 967d1f9 | 2011-07-18 13:03:04 -0400 | [diff] [blame] | 12 | #include <linux/percpu.h> |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 13 | #include <linux/hardirq.h> |
Chris Metcalf | ef1f098 | 2012-04-11 12:21:39 -0400 | [diff] [blame] | 14 | #include <linux/irqflags.h> |
Steven Rostedt | c0e980a | 2012-11-15 11:34:21 -0500 | [diff] [blame] | 15 | #include <linux/cpu.h> |
| 16 | #include <linux/notifier.h> |
Paul Gortmaker | 967d1f9 | 2011-07-18 13:03:04 -0400 | [diff] [blame] | 17 | #include <asm/processor.h> |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 18 | |
| 19 | /* |
| 20 | * An entry can be in one of four states: |
| 21 | * |
| 22 | * free NULL, 0 -> {claimed} : free to be used |
| 23 | * claimed NULL, 3 -> {pending} : claimed to be enqueued |
| 24 | * pending next, 3 -> {busy} : queued, pending callback |
| 25 | * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 26 | */ |
| 27 | |
| 28 | #define IRQ_WORK_PENDING 1UL |
| 29 | #define IRQ_WORK_BUSY 2UL |
| 30 | #define IRQ_WORK_FLAGS 3UL |
| 31 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 32 | static DEFINE_PER_CPU(struct llist_head, irq_work_list); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 33 | |
| 34 | /* |
| 35 | * Claim the entry so that no one else will poke at it. |
| 36 | */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 37 | static bool irq_work_claim(struct irq_work *work) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 38 | { |
Frederic Weisbecker | e0bbe2d | 2012-10-27 15:21:36 +0200 | [diff] [blame] | 39 | unsigned long flags, oflags, nflags; |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 40 | |
Frederic Weisbecker | e0bbe2d | 2012-10-27 15:21:36 +0200 | [diff] [blame] | 41 | /* |
| 42 | * Start with our best wish as a premise but only trust any |
| 43 | * flag value after cmpxchg() result. |
| 44 | */ |
| 45 | flags = work->flags & ~IRQ_WORK_PENDING; |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 46 | for (;;) { |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 47 | nflags = flags | IRQ_WORK_FLAGS; |
Frederic Weisbecker | e0bbe2d | 2012-10-27 15:21:36 +0200 | [diff] [blame] | 48 | oflags = cmpxchg(&work->flags, flags, nflags); |
| 49 | if (oflags == flags) |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 50 | break; |
Frederic Weisbecker | e0bbe2d | 2012-10-27 15:21:36 +0200 | [diff] [blame] | 51 | if (oflags & IRQ_WORK_PENDING) |
| 52 | return false; |
| 53 | flags = oflags; |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 54 | cpu_relax(); |
| 55 | } |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 56 | |
| 57 | return true; |
| 58 | } |
| 59 | |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 60 | void __weak arch_irq_work_raise(void) |
| 61 | { |
| 62 | /* |
| 63 | * Lame architectures will get the timer tick callback |
| 64 | */ |
| 65 | } |
| 66 | |
| 67 | /* |
| 68 | * Queue the entry and raise the IPI if needed. |
| 69 | */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 70 | static void __irq_work_queue(struct irq_work *work) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 71 | { |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 72 | bool empty; |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 73 | |
Christoph Lameter | 20b8769 | 2010-12-14 10:28:45 -0600 | [diff] [blame] | 74 | preempt_disable(); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 75 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 76 | empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list)); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 77 | /* The list was empty, raise self-interrupt to start processing. */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 78 | if (empty) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 79 | arch_irq_work_raise(); |
| 80 | |
Christoph Lameter | 20b8769 | 2010-12-14 10:28:45 -0600 | [diff] [blame] | 81 | preempt_enable(); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 82 | } |
| 83 | |
| 84 | /* |
| 85 | * Enqueue the irq_work @entry, returns true on success, failure when the |
| 86 | * @entry was already enqueued by someone else. |
| 87 | * |
| 88 | * Can be re-enqueued while the callback is still in progress. |
| 89 | */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 90 | bool irq_work_queue(struct irq_work *work) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 91 | { |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 92 | if (!irq_work_claim(work)) { |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 93 | /* |
| 94 | * Already enqueued, can't do! |
| 95 | */ |
| 96 | return false; |
| 97 | } |
| 98 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 99 | __irq_work_queue(work); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 100 | return true; |
| 101 | } |
| 102 | EXPORT_SYMBOL_GPL(irq_work_queue); |
| 103 | |
Frederic Weisbecker | 00b4295 | 2012-11-07 21:03:07 +0100 | [diff] [blame] | 104 | bool irq_work_needs_cpu(void) |
| 105 | { |
| 106 | struct llist_head *this_list; |
| 107 | |
| 108 | this_list = &__get_cpu_var(irq_work_list); |
| 109 | if (llist_empty(this_list)) |
| 110 | return false; |
| 111 | |
Steven Rostedt | 8aa2acc | 2012-11-15 12:52:44 -0500 | [diff] [blame^] | 112 | /* All work should have been flushed before going offline */ |
| 113 | WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
| 114 | |
Frederic Weisbecker | 00b4295 | 2012-11-07 21:03:07 +0100 | [diff] [blame] | 115 | return true; |
| 116 | } |
| 117 | |
Steven Rostedt | c0e980a | 2012-11-15 11:34:21 -0500 | [diff] [blame] | 118 | static void __irq_work_run(void) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 119 | { |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 120 | struct irq_work *work; |
| 121 | struct llist_head *this_list; |
| 122 | struct llist_node *llnode; |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 123 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 124 | this_list = &__get_cpu_var(irq_work_list); |
| 125 | if (llist_empty(this_list)) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 126 | return; |
| 127 | |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 128 | BUG_ON(!irqs_disabled()); |
| 129 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 130 | llnode = llist_del_all(this_list); |
| 131 | while (llnode != NULL) { |
| 132 | work = llist_entry(llnode, struct irq_work, llnode); |
Christoph Lameter | 20b8769 | 2010-12-14 10:28:45 -0600 | [diff] [blame] | 133 | |
Peter Zijlstra | 924f8f5 | 2011-09-12 13:12:28 +0200 | [diff] [blame] | 134 | llnode = llist_next(llnode); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 135 | |
| 136 | /* |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 137 | * Clear the PENDING bit, after this point the @work |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 138 | * can be re-used. |
Frederic Weisbecker | c8446b7 | 2012-10-30 13:33:54 +0100 | [diff] [blame] | 139 | * Make it immediately visible so that other CPUs trying |
| 140 | * to claim that work don't rely on us to handle their data |
| 141 | * while we are in the middle of the func. |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 142 | */ |
Frederic Weisbecker | c8446b7 | 2012-10-30 13:33:54 +0100 | [diff] [blame] | 143 | xchg(&work->flags, IRQ_WORK_BUSY); |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 144 | work->func(work); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 145 | /* |
| 146 | * Clear the BUSY bit and return to the free state if |
| 147 | * no-one else claimed it meanwhile. |
| 148 | */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 149 | (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0); |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 150 | } |
| 151 | } |
Steven Rostedt | c0e980a | 2012-11-15 11:34:21 -0500 | [diff] [blame] | 152 | |
| 153 | /* |
| 154 | * Run the irq_work entries on this cpu. Requires to be ran from hardirq |
| 155 | * context with local IRQs disabled. |
| 156 | */ |
| 157 | void irq_work_run(void) |
| 158 | { |
| 159 | BUG_ON(!in_irq()); |
| 160 | __irq_work_run(); |
| 161 | } |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 162 | EXPORT_SYMBOL_GPL(irq_work_run); |
| 163 | |
| 164 | /* |
| 165 | * Synchronize against the irq_work @entry, ensures the entry is not |
| 166 | * currently in use. |
| 167 | */ |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 168 | void irq_work_sync(struct irq_work *work) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 169 | { |
| 170 | WARN_ON_ONCE(irqs_disabled()); |
| 171 | |
Huang Ying | 38aaf80 | 2011-09-08 14:00:46 +0800 | [diff] [blame] | 172 | while (work->flags & IRQ_WORK_BUSY) |
Peter Zijlstra | e360adb | 2010-10-14 14:01:34 +0800 | [diff] [blame] | 173 | cpu_relax(); |
| 174 | } |
| 175 | EXPORT_SYMBOL_GPL(irq_work_sync); |
Steven Rostedt | c0e980a | 2012-11-15 11:34:21 -0500 | [diff] [blame] | 176 | |
| 177 | #ifdef CONFIG_HOTPLUG_CPU |
| 178 | static int irq_work_cpu_notify(struct notifier_block *self, |
| 179 | unsigned long action, void *hcpu) |
| 180 | { |
| 181 | long cpu = (long)hcpu; |
| 182 | |
| 183 | switch (action) { |
| 184 | case CPU_DYING: |
| 185 | /* Called from stop_machine */ |
| 186 | if (WARN_ON_ONCE(cpu != smp_processor_id())) |
| 187 | break; |
| 188 | __irq_work_run(); |
| 189 | break; |
| 190 | default: |
| 191 | break; |
| 192 | } |
| 193 | return NOTIFY_OK; |
| 194 | } |
| 195 | |
| 196 | static struct notifier_block cpu_notify; |
| 197 | |
| 198 | static __init int irq_work_init_cpu_notifier(void) |
| 199 | { |
| 200 | cpu_notify.notifier_call = irq_work_cpu_notify; |
| 201 | cpu_notify.priority = 0; |
| 202 | register_cpu_notifier(&cpu_notify); |
| 203 | return 0; |
| 204 | } |
| 205 | device_initcall(irq_work_init_cpu_notifier); |
| 206 | |
| 207 | #endif /* CONFIG_HOTPLUG_CPU */ |