[POWERPC] Fix irq enable/disable in smp_generic_take_timebase

Eran Ben-Avi <eranpublic@yahoo.com> pointed out that the arch/ppc version
of smp_generic_take_timebase disables interrupts on entry but exits without
restoring them.  However, both it and the arch/powerpc version have another
problem, which is that they use local_irq_disable/enable rather than
local_irq_save/restore, and they are called with interrupts disabled.

This fixes both problems; it changes a return to a break in the arch/ppc
version, and changes both versions to use local_irq_save/restore.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/smp-tbsync.c

@@ -45,8 +45,9 @@ void __devinit smp_generic_take_timebase(void)
 {
 	int cmd;
 	u64 tb;
+	unsigned long flags;
 
-	local_irq_disable();
+	local_irq_save(flags);
 	while (!running)
 		barrier();
 	rmb();
@@ -70,7 +71,7 @@ void __devinit smp_generic_take_timebase(void)
 			set_tb(tb >> 32, tb & 0xfffffffful);
 		enter_contest(tbsync->mark, -1);
 	}
-	local_irq_enable();
+	local_irq_restore(flags);
 }
 
 static int __devinit start_contest(int cmd, long offset, int num)

arch/ppc/kernel/smp-tbsync.c

@@ -47,8 +47,9 @@ void __devinit
 smp_generic_take_timebase( void )
 {
 	int cmd, tbl, tbu;
+	unsigned long flags;
 
-	local_irq_disable();
+	local_irq_save(flags);
 	while( !running )
 		;
 	rmb();
@@ -64,7 +65,7 @@ smp_generic_take_timebase( void )
 		tbu = tbsync->tbu;
 		tbsync->ack = 0;
 		if( cmd == kExit )
-			return;
+			break;
 
 		if( cmd == kSetAndTest ) {
 			while( tbsync->handshake )
@@ -77,7 +78,7 @@ smp_generic_take_timebase( void )
 		}
 		enter_contest( tbsync->mark, -1 );
 	}
-	local_irq_enable();
+	local_irq_restore(flags);
 }
 
 static int __devinit