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Commit ee238713 authored by Ivo Sieben's avatar Ivo Sieben Committed by Thomas Gleixner
Browse files

genirq: Set irq thread to RT priority on creation 



When a threaded irq handler is installed the irq thread is initially
created on normal scheduling priority. Only after the irq thread is
woken up it sets its priority to RT_FIFO MAX_USER_RT_PRIO/2 itself.

This means that interrupts that occur directly after the irq handler
is installed will be handled on a normal scheduling priority instead
of the realtime priority that one would expect.

Fix this by setting the RT priority on creation of the irq_thread.

Signed-off-by: default avatarIvo Sieben <meltedpianoman@gmail.com>
Cc: Sebastian Andrzej Siewior  <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1370254322-17240-1-git-send-email-meltedpianoman@gmail.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 9dbd90f1

kernel/irq/manage.c

+6 −5
Original line number Diff line number Diff line
@@ -840,9 +840,6 @@ static void irq_thread_dtor(struct callback_head *unused) 
static int irq_thread(void *data)

{

	struct callback_head on_exit_work;

	static const struct sched_param param = {

		.sched_priority = MAX_USER_RT_PRIO/2,

	};

	struct irqaction *action = data;

	struct irq_desc *desc = irq_to_desc(action->irq);

	irqreturn_t (*handler_fn)(struct irq_desc *desc,
@@ -854,8 +851,6 @@ static int irq_thread(void *data) 
	else

		handler_fn = irq_thread_fn;



	sched_setscheduler(current, SCHED_FIFO, &param);



	init_task_work(&on_exit_work, irq_thread_dtor);

	task_work_add(current, &on_exit_work, false);
@@ -950,6 +945,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) 
	 */

	if (new->thread_fn && !nested) {

		struct task_struct *t;

		static const struct sched_param param = {

			.sched_priority = MAX_USER_RT_PRIO/2,

		};



		t = kthread_create(irq_thread, new, "irq/%d-%s", irq,

				   new->name);
@@ -957,6 +955,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new) 
			ret = PTR_ERR(t);

			goto out_mput;

		}



		sched_setscheduler(t, SCHED_FIFO, &param);



		/*

		 * We keep the reference to the task struct even if

		 * the thread dies to avoid that the interrupt code