task_work: make TWA_NMI_CURRENT handling conditional on IRQ_WORK

The TWA_NMI_CURRENT handling very much depends on IRQ_WORK, but that
isn't universally enabled everywhere.

Maybe the IRQ_WORK infrastructure should just be unconditional - x86
ends up indirectly enabling it through unconditionally enabling
PERF_EVENTS, for example.  But it also gets enabled by having SMP
support, or even if you just have PRINTK enabled.

But in the meantime TWA_NMI_CURRENT causes tons of build failures on
various odd minimal configs.  Which did show up in linux-next, but
despite that nobody bothered to fix it or even inform me until -rc1 was
out.

Fixes: 466e4d801cd4 ("task_work: Add TWA_NMI_CURRENT as an additional notify mode")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 5c2daa7ad3f906aefa5a521b36ce49d30257725d..5d14d639ac71b54a24dac49acd02f6c2c7e58e04 100644 (file)
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -6,12 +6,14 @@
 
 static struct callback_head work_exited; /* all we need is ->next == NULL */
 
+#ifdef CONFIG_IRQ_WORK
 static void task_work_set_notify_irq(struct irq_work *entry)
 {
        test_and_set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
 }
 static DEFINE_PER_CPU(struct irq_work, irq_work_NMI_resume) =
        IRQ_WORK_INIT_HARD(task_work_set_notify_irq);
+#endif
 
 /**
  * task_work_add - ask the @task to execute @work->func()
@@ -57,6 +59,8 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
        if (notify == TWA_NMI_CURRENT) {
                if (WARN_ON_ONCE(task != current))
                        return -EINVAL;
+               if (!IS_ENABLED(CONFIG_IRQ_WORK))
+                       return -EINVAL;
        } else {
                /* record the work call stack in order to print it in KASAN reports */
                kasan_record_aux_stack(work);
@@ -81,9 +85,11 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
        case TWA_SIGNAL_NO_IPI:
                __set_notify_signal(task);
                break;
+#ifdef CONFIG_IRQ_WORK
        case TWA_NMI_CURRENT:
                irq_work_queue(this_cpu_ptr(&irq_work_NMI_resume));
                break;
+#endif
        default:
                WARN_ON_ONCE(1);
                break;