tile: Reorganize _switch_to()

Move the simulator bits into finish_arch_post_lock_switch() and
properly call __switch_to() from _switch_to().

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: <efault@gmx.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1438783412-10990-1-git-send-email-cmetcalf@ezchip.com
[ Made it a delta to: fe363adb9225 ("sched, tile: Remove finish_arch_switch"). ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/tile/include/asm/switch_to.h

@@ -56,6 +56,8 @@ extern unsigned long get_switch_to_pc(void);
  * We defer homecache migration until the runqueue lock is released.
  */
 #define finish_arch_post_lock_switch() do {                               \
+	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_SWITCH |             \
+		(current->pid << _SIM_CONTROL_OPERATOR_BITS));            \
 	if (current->mm == NULL && !kstack_hash &&                        \
 	    current_thread_info()->homecache_cpu != raw_smp_processor_id()) \
 		homecache_migrate_kthread();                              \

arch/tile/kernel/process.c

@@ -446,26 +446,18 @@ struct task_struct *__sched _switch_to(struct task_struct *prev,
 	hardwall_switch_tasks(prev, next);
 #endif
 
-	/*
-	 * Switch kernel SP, PC, and callee-saved registers.
-	 * Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
-	 * Once we return from this function we will have changed stacks
-	 * and be running with current == next.
-	 */
-	__switch_to(prev, next, next_current_ksp0(next));
-
-	/* Notify the simulator of task switch and task exit. */
+	/* Notify the simulator of task exit. */
 	if (unlikely(prev->state == TASK_DEAD))
 		__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_EXIT |
 			     (prev->pid << _SIM_CONTROL_OPERATOR_BITS));
-	__insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_SWITCH |
-		(next->pid << _SIM_CONTROL_OPERATOR_BITS));
 
 	/*
+	 * Switch kernel SP, PC, and callee-saved registers.
 	 * In the context of the new task, return the old task pointer
 	 * (i.e. the task that actually called __switch_to).
+	 * Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
 	 */
-	return prev;
+	return __switch_to(prev, next, next_current_ksp0(next));
 }
 
 /*