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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: Ivo 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: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Ivo Sieben 2013-06-03 12:12:02 +02:00 committed by Thomas Gleixner
parent 9dbd90f17e
commit ee23871389
1 changed files with 6 additions and 5 deletions
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11
kernel/irq/manage.c
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@ -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