genirq: Get rid of unnecessary irqaction field in task_struct

When a new thread handler is created, an irqaction is passed to it as
data. Not only that irqaction is stored in task_struct by the handler
for later use, but also a structure associated with the kernel thread
keeps this value as long as the thread exists.

This fix kicks irqaction out off task_struct. Yes, I introduce new bit
field. But it allows not only to eliminate the duplicate, but also
shortens size of task_struct.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Link: http://lkml.kernel.org/r/20120309135925.GB2114@dhcp-26-207.brq.redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7d379a6bfd886679fcfefee2ed90fb636d6cd028..07f537a371ce1b2d58acf1745692dc3155ae3b7f 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1319,6 +1319,11 @@ struct task_struct {
        unsigned sched_reset_on_fork:1;
        unsigned sched_contributes_to_load:1;
 
+#ifdef CONFIG_GENERIC_HARDIRQS
+       /* IRQ handler threads */
+       unsigned irq_thread:1;
+#endif
+
        pid_t pid;
        pid_t tgid;
 
@@ -1427,11 +1432,6 @@ struct task_struct {
  * mempolicy */
        spinlock_t alloc_lock;
 
-#ifdef CONFIG_GENERIC_HARDIRQS
-       /* IRQ handler threads */
-       struct irqaction *irqaction;
-#endif
-
        /* Protection of the PI data structures: */
        raw_spinlock_t pi_lock;
 

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index c0730ad8a1173960f0ffa368dcf46140166ccddb..0fa3ce998ecbfd57fc0fa2b1c3c17595c9b6f037 100644 (file)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -780,7 +780,7 @@ static int irq_thread(void *data)
                handler_fn = irq_thread_fn;
 
        sched_setscheduler(current, SCHED_FIFO, &param);
-       current->irqaction = action;
+       current->irq_thread = 1;
 
        while (!irq_wait_for_interrupt(action)) {
 
@@ -818,10 +818,10 @@ static int irq_thread(void *data)
        irq_finalize_oneshot(desc, action, true);
 
        /*
-        * Clear irqaction. Otherwise exit_irq_thread() would make
+        * Clear irq_thread. Otherwise exit_irq_thread() would make
         * fuzz about an active irq thread going into nirvana.
         */
-       current->irqaction = NULL;
+       current->irq_thread = 0;
        return 0;
 }
 
@@ -832,27 +832,30 @@ void exit_irq_thread(void)
 {
        struct task_struct *tsk = current;
        struct irq_desc *desc;
+       struct irqaction *action;
 
-       if (!tsk->irqaction)
+       if (!tsk->irq_thread)
                return;
 
+       action = kthread_data(tsk);
+
        printk(KERN_ERR
               "exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
-              tsk->comm ? tsk->comm : "", tsk->pid, tsk->irqaction->irq);
+              tsk->comm ? tsk->comm : "", tsk->pid, action->irq);
 
-       desc = irq_to_desc(tsk->irqaction->irq);
+       desc = irq_to_desc(action->irq);
 
        /*
         * Prevent a stale desc->threads_oneshot. Must be called
         * before setting the IRQTF_DIED flag.
         */
-       irq_finalize_oneshot(desc, tsk->irqaction, true);
+       irq_finalize_oneshot(desc, action, true);
 
        /*
         * Set the THREAD DIED flag to prevent further wakeups of the
         * soon to be gone threaded handler.
         */
-       set_bit(IRQTF_DIED, &tsk->irqaction->flags);
+       set_bit(IRQTF_DIED, &action->flags);
 }
 
 static void irq_setup_forced_threading(struct irqaction *new)