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authorFrederic Weisbecker <fweisbec@gmail.com>2013-02-05 00:48:46 +0100
committerFrederic Weisbecker <fweisbec@gmail.com>2013-02-05 00:48:46 +0100
commit077931446b85e7858bf9dc0927cd116669b965d2 (patch)
tree02fbdf4a42b30b841a61aca399bd0ac6a5c308e6 /kernel/irq_work.c
parentf7c819c020db9796ae3a662b82a310617f92b15b (diff)
parent74876a98a87a115254b3a66a14b27320b7f0acaa (diff)
downloadlinux-sh-077931446b85e7858bf9dc0927cd116669b965d2.tar.gz
Merge branch 'nohz/printk-v8' into irq/core
Conflicts: kernel/irq_work.c Add support for printk in full dynticks CPU. * Don't stop tick with irq works pending. This fix is generally useful and concerns archs that can't raise self IPIs. * Flush irq works before CPU offlining. * Introduce "lazy" irq works that can wait for the next tick to be executed, unless it's stopped. * Implement klogd wake up using irq work. This removes the ad-hoc printk_tick()/printk_needs_cpu() hooks and make it working even in dynticks mode. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'kernel/irq_work.c')
-rw-r--r--kernel/irq_work.c112
1 files changed, 86 insertions, 26 deletions
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index c9d7478e4889..55fcce6065cf 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -12,22 +12,15 @@
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
#include <asm/processor.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
- */
-
-#define IRQ_WORK_PENDING 1UL
-#define IRQ_WORK_BUSY 2UL
-#define IRQ_WORK_FLAGS 3UL
static DEFINE_PER_CPU(struct llist_head, irq_work_list);
+static DEFINE_PER_CPU(int, irq_work_raised);
/*
* Claim the entry so that no one else will poke at it.
@@ -70,8 +63,6 @@ void __weak arch_irq_work_raise(void)
*/
void irq_work_queue(struct irq_work *work)
{
- bool empty;
-
/* Only queue if not already pending */
if (!irq_work_claim(work))
return;
@@ -79,30 +70,55 @@ void irq_work_queue(struct irq_work *work)
/* Queue the entry and raise the IPI if needed. */
preempt_disable();
- empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
- /* The list was empty, raise self-interrupt to start processing. */
- if (empty)
- arch_irq_work_raise();
+ llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
+
+ /*
+ * If the work is not "lazy" or the tick is stopped, raise the irq
+ * work interrupt (if supported by the arch), otherwise, just wait
+ * for the next tick.
+ */
+ if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
+ if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
+ arch_irq_work_raise();
+ }
preempt_enable();
}
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)
+bool irq_work_needs_cpu(void)
+{
+ struct llist_head *this_list;
+
+ this_list = &__get_cpu_var(irq_work_list);
+ if (llist_empty(this_list))
+ return false;
+
+ /* All work should have been flushed before going offline */
+ WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+
+ return true;
+}
+
+static void __irq_work_run(void)
{
+ unsigned long flags;
struct irq_work *work;
struct llist_head *this_list;
struct llist_node *llnode;
+
+ /*
+ * Reset the "raised" state right before we check the list because
+ * an NMI may enqueue after we find the list empty from the runner.
+ */
+ __this_cpu_write(irq_work_raised, 0);
+ barrier();
+
this_list = &__get_cpu_var(irq_work_list);
if (llist_empty(this_list))
return;
- BUG_ON(!in_irq());
BUG_ON(!irqs_disabled());
llnode = llist_del_all(this_list);
@@ -118,15 +134,27 @@ void irq_work_run(void)
* to claim that work don't rely on us to handle their data
* while we are in the middle of the func.
*/
- xchg(&work->flags, IRQ_WORK_BUSY);
+ flags = work->flags & ~IRQ_WORK_PENDING;
+ xchg(&work->flags, flags);
+
work->func(work);
/*
* Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile.
*/
- (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
+ (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
}
}
+
+/*
+ * Run the irq_work entries on this cpu. Requires to be ran from hardirq
+ * context with local IRQs disabled.
+ */
+void irq_work_run(void)
+{
+ BUG_ON(!in_irq());
+ __irq_work_run();
+}
EXPORT_SYMBOL_GPL(irq_work_run);
/*
@@ -141,3 +169,35 @@ void irq_work_sync(struct irq_work *work)
cpu_relax();
}
EXPORT_SYMBOL_GPL(irq_work_sync);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int irq_work_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ long cpu = (long)hcpu;
+
+ switch (action) {
+ case CPU_DYING:
+ /* Called from stop_machine */
+ if (WARN_ON_ONCE(cpu != smp_processor_id()))
+ break;
+ __irq_work_run();
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_notify;
+
+static __init int irq_work_init_cpu_notifier(void)
+{
+ cpu_notify.notifier_call = irq_work_cpu_notify;
+ cpu_notify.priority = 0;
+ register_cpu_notifier(&cpu_notify);
+ return 0;
+}
+device_initcall(irq_work_init_cpu_notifier);
+
+#endif /* CONFIG_HOTPLUG_CPU */