debugobjects: Make them PREEMPT_RT aware

On PREEMPT_RT enabled kernels it is not possible to refill the object pool
from atomic context (preemption or interrupts disabled) as the allocator
might acquire 'sleeping' spinlocks.

Guard the invocation of fill_pool() accordingly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/87sfzehdnl.ffs@tglx

lib/debugobjects.c

@@ -557,7 +557,12 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack
 	struct debug_obj *obj;
 	unsigned long flags;
 
-	fill_pool();
+	/*
+	 * On RT enabled kernels the pool refill must happen in preemptible
+	 * context:
+	 */
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
+		fill_pool();
 
 	db = get_bucket((unsigned long) addr);