irq_work: Warn if there's still work on cpu_down

If we are in nohz and there's still irq_work to be done when the idle
task is about to go offline, give a nasty warning. Everything should
have been flushed from the CPU_DYING notifier already. Further attempts
to enqueue an irq_work are buggy because irqs are disabled by
__cpu_disable(). The best we can do is to report the issue to the user.

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>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 4ed17490f629..480f74715ba9 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -109,6 +109,9 @@ bool irq_work_needs_cpu(void)
         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;
 }