irq_work: Flush work on CPU_DYING

In order not to offline a CPU with pending irq works, flush the
queue from CPU_DYING. The notifier is called by stop_machine on
the CPU that is going down. The code will not be called from irq context
(so things like get_irq_regs() wont work) but I'm not sure what the
requirements are for irq_work in that regard (Peter?). But irqs are
disabled and the CPU is about to go offline. Might as well flush the work.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index b3c113a14727211356b20c3cdaa3771bb611cb39..4ed17490f6299cf67ea40e41ee03b7351dad4163 100644 (file)
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -12,6 +12,8 @@
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
 #include <asm/processor.h>
 
 /*
@@ -110,11 +112,7 @@ bool irq_work_needs_cpu(void)
        return true;
 }
 
-/*
- * Run the irq_work entries on this cpu. Requires to be ran from hardirq
- * context with local IRQs disabled.
- */
-void irq_work_run(void)
+static void __irq_work_run(void)
 {
        struct irq_work *work;
        struct llist_head *this_list;
@@ -124,7 +122,6 @@ void irq_work_run(void)
        if (llist_empty(this_list))
                return;
 
-       BUG_ON(!in_irq());
        BUG_ON(!irqs_disabled());
 
        llnode = llist_del_all(this_list);
@@ -149,6 +146,16 @@ void irq_work_run(void)
                (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
        }
 }
+
+/*
+ * 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);
 
 /*
@@ -163,3 +170,35 @@ 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 */