sched: remove sleep_on() and friends

This is the final piece in the puzzle, as all patches to remove the
last users of \(interruptible_\|\)sleep_on\(_timeout\|\) have made it
into the 3.15 merge window. The work was long overdue, and this
interface in particular should not have survived the BKL removal
that was done a couple of years ago.

Citing Jon Corbet from http://lwn.net/2001/0201/kernel.php3":

 "[...] it was suggested that the janitors look for and fix all code
  that calls sleep_on() [...] since (1) almost all such code is
  incorrect, and (2) Linus has agreed that those functions should
  be removed in the 2.5 development series".

We haven't quite made it for 2.5, but maybe we can merge this for 3.15.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/DocBook/kernel-hacking.tmpl

@@ -850,16 +850,6 @@ printk(KERN_INFO "my ip: %pI4\n", &ipaddress);
     <returnvalue>-ERESTARTSYS</returnvalue> if a signal is received.
     The <function>wait_event()</function> version ignores signals.
    </para>
-   <para>
-   Do not use the <function>sleep_on()</function> function family -
-   it is very easy to accidentally introduce races; almost certainly
-   one of the <function>wait_event()</function> family will do, or a
-   loop around <function>schedule_timeout()</function>. If you choose
-   to loop around <function>schedule_timeout()</function> remember
-   you must set the task state (with 
-   <function>set_current_state()</function>) on each iteration to avoid
-   busy-looping.
-   </para>
  
   </sect1>
 

include/linux/wait.h

@@ -803,17 +803,6 @@ do {									\
 	__ret;								\
 })
 
-
-/*
- * These are the old interfaces to sleep waiting for an event.
- * They are racy.  DO NOT use them, use the wait_event* interfaces above.
- * We plan to remove these interfaces.
- */
-extern void sleep_on(wait_queue_head_t *q);
-extern long sleep_on_timeout(wait_queue_head_t *q, signed long timeout);
-extern void interruptible_sleep_on(wait_queue_head_t *q);
-extern long interruptible_sleep_on_timeout(wait_queue_head_t *q, signed long timeout);
-
 /*
  * Waitqueues which are removed from the waitqueue_head at wakeup time
  */

kernel/sched/core.c

@@ -2845,52 +2845,6 @@ int default_wake_function(wait_queue_t *curr, unsigned mode, int wake_flags,
 }
 EXPORT_SYMBOL(default_wake_function);
 
-static long __sched
-sleep_on_common(wait_queue_head_t *q, int state, long timeout)
-{
-	unsigned long flags;
-	wait_queue_t wait;
-
-	init_waitqueue_entry(&wait, current);
-
-	__set_current_state(state);
-
-	spin_lock_irqsave(&q->lock, flags);
-	__add_wait_queue(q, &wait);
-	spin_unlock(&q->lock);
-	timeout = schedule_timeout(timeout);
-	spin_lock_irq(&q->lock);
-	__remove_wait_queue(q, &wait);
-	spin_unlock_irqrestore(&q->lock, flags);
-
-	return timeout;
-}
-
-void __sched interruptible_sleep_on(wait_queue_head_t *q)
-{
-	sleep_on_common(q, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
-}
-EXPORT_SYMBOL(interruptible_sleep_on);
-
-long __sched
-interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
-{
-	return sleep_on_common(q, TASK_INTERRUPTIBLE, timeout);
-}
-EXPORT_SYMBOL(interruptible_sleep_on_timeout);
-
-void __sched sleep_on(wait_queue_head_t *q)
-{
-	sleep_on_common(q, TASK_UNINTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
-}
-EXPORT_SYMBOL(sleep_on);
-
-long __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
-{
-	return sleep_on_common(q, TASK_UNINTERRUPTIBLE, timeout);
-}
-EXPORT_SYMBOL(sleep_on_timeout);
-
 #ifdef CONFIG_RT_MUTEXES
 
 /*