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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 29 Jul 2024 12:05:06 -0700
Subject: [PATCH] task_work: make TWA_NMI_CURRENT handling conditional on
IRQ_WORK
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz
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>
---
kernel/task_work.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -7,12 +7,14 @@
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()
@@ -58,6 +60,8 @@ int task_work_add(struct task_struct *ta
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);
@@ -82,9 +86,11 @@ int task_work_add(struct task_struct *ta
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;
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