sched: Separate the scheduler entry for preemption

Block-IO and workqueues call into notifier functions from the
scheduler core code with interrupts and preemption disabled. These
calls should be made before entering the scheduler core.

To simplify this, separate the scheduler core code into
__schedule(). __schedule() is directly called from the places which
set PREEMPT_ACTIVE and from schedule(). This allows us to add the work
checks into schedule(), so they are only called when a task voluntary
goes to sleep.

Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: [email protected] # 2.6.39+
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/sched.c b/kernel/sched.c
index ccacdbdecf452bda8769878ca6e558d13ebb4e74..ec15e8129cf74e8255d6dd1a3c67553fa2c1217e 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4279,9 +4279,9 @@ pick_next_task(struct rq *rq)
 }
 
 /*
- * schedule() is the main scheduler function.
+ * __schedule() is the main scheduler function.
  */
-asmlinkage void __sched schedule(void)
+static void __sched __schedule(void)
 {
        struct task_struct *prev, *next;
        unsigned long *switch_count;
@@ -4369,6 +4369,11 @@ need_resched:
        if (need_resched())
                goto need_resched;
 }
+
+asmlinkage void schedule(void)
+{
+       __schedule();
+}
 EXPORT_SYMBOL(schedule);
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
@@ -4435,7 +4440,7 @@ asmlinkage void __sched notrace preempt_schedule(void)
 
        do {
                add_preempt_count_notrace(PREEMPT_ACTIVE);
-               schedule();
+               __schedule();
                sub_preempt_count_notrace(PREEMPT_ACTIVE);
 
                /*
@@ -4463,7 +4468,7 @@ asmlinkage void __sched preempt_schedule_irq(void)
        do {
                add_preempt_count(PREEMPT_ACTIVE);
                local_irq_enable();
-               schedule();
+               __schedule();
                local_irq_disable();
                sub_preempt_count(PREEMPT_ACTIVE);
 
@@ -5588,7 +5593,7 @@ static inline int should_resched(void)
 static void __cond_resched(void)
 {
        add_preempt_count(PREEMPT_ACTIVE);
-       schedule();
+       __schedule();
        sub_preempt_count(PREEMPT_ACTIVE);
 }