sched: Separate the scheduler entry for preemption

commit c259e01a1ec90063042f758e409cd26b2a0963c8 upstream.

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 <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110622174918.813258321@linutronix.de
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/sched.c b/kernel/sched.c
index fde6ff90352583d65ff890a407200f2fb0c3073e..64f93d18e4d4bfafd07e269cbbc4cf74a6a225be 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4242,9 +4242,9 @@ 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;
@@ -4332,6 +4332,11 @@ need_resched:
        if (need_resched())
                goto need_resched;
 }
+
+asmlinkage void schedule(void)
+{
+       __schedule();
+}
 EXPORT_SYMBOL(schedule);
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
@@ -4405,7 +4410,7 @@ asmlinkage void __sched notrace preempt_schedule(void)
 
        do {
                add_preempt_count_notrace(PREEMPT_ACTIVE);
-               schedule();
+               __schedule();
                sub_preempt_count_notrace(PREEMPT_ACTIVE);
 
                /*
@@ -4433,7 +4438,7 @@ 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);
 
@@ -5558,7 +5563,7 @@ static inline int should_resched(void)
 static void __cond_resched(void)
 {
        add_preempt_count(PREEMPT_ACTIVE);
-       schedule();
+       __schedule();
        sub_preempt_count(PREEMPT_ACTIVE);
 }