irq_work: Remove BUG_ON in irq_work_run()

Because of a collision with 8d056c48e486 ("CPU hotplug, smp: flush any
pending IPI callbacks before CPU offline"), which ends up calling
hotplug_cfd()->flush_smp_call_function_queue()->irq_work_run(), which
is not from IRQ context.

And since that already calls irq_work_run() from the hotplug path,
remove our entire hotplug handling.

Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 4 insertions, 42 deletions

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 4b0a890a304a..e6bcbe756663 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -160,20 +160,14 @@ static void irq_work_run_list(struct llist_head *list)
         }
 }
 
-static void __irq_work_run(void)
-{
-        irq_work_run_list(&__get_cpu_var(raised_list));
-        irq_work_run_list(&__get_cpu_var(lazy_list));
-}
-
 /*
- * Run the irq_work entries on this cpu. Requires to be ran from hardirq
- * context with local IRQs disabled.
+ * hotplug calls this through:
+ *  hotplug_cfd() -> flush_smp_call_function_queue()
  */
 void irq_work_run(void)
 {
-        BUG_ON(!in_irq());
-        __irq_work_run();
+        irq_work_run_list(&__get_cpu_var(raised_list));
+        irq_work_run_list(&__get_cpu_var(lazy_list));
 }
 EXPORT_SYMBOL_GPL(irq_work_run);
 
@@ -189,35 +183,3 @@ 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 */