genirq: Remove cpumask availability check on kthread affinity setting

Failing to allocate the affinity mask of an interrupt descriptor fails the
whole descriptor initialization. It is then guaranteed that the cpumask is
always available whenever the related interrupt objects are alive, such as
the kthread handler.

Therefore remove the superfluous check since it is merely a historical
leftover. Get rid also of the comments above it that are obsolete and
useless.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251121143500.42111-4-frederic@kernel.org

Author: Frederic Weisbecker

kernel/irq/manage.c

@@ -1001,7 +1001,6 @@ static irqreturn_t irq_forced_secondary_handler(int irq, void *dev_id)
 static void irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action)
 {
 	cpumask_var_t mask;
-	bool valid = false;
 
 	if (!test_and_clear_bit(IRQTF_AFFINITY, &action->thread_flags))
 		return;
@@ -1018,21 +1017,13 @@ static void irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *a
 	}
 
 	scoped_guard(raw_spinlock_irq, &desc->lock) {
-		/*
-		 * This code is triggered unconditionally. Check the affinity
-		 * mask pointer. For CPU_MASK_OFFSTACK=n this is optimized out.
-		 */
-		if (cpumask_available(desc->irq_common_data.affinity)) {
-			const struct cpumask *m;
+		const struct cpumask *m;
 
-			m = irq_data_get_effective_affinity_mask(&desc->irq_data);
-			cpumask_copy(mask, m);
-			valid = true;
-		}
+		m = irq_data_get_effective_affinity_mask(&desc->irq_data);
+		cpumask_copy(mask, m);
 	}
 
-	if (valid)
-		set_cpus_allowed_ptr(current, mask);
+	set_cpus_allowed_ptr(current, mask);
 	free_cpumask_var(mask);
 }
 #else