hrtimer: don't modify restart_block->fn in restart functions

hrtimer_nanosleep_restart() clears/restores restart_block->fn. This is
pointless and complicates its usage. Note that if sys_restart_syscall()
doesn't actually happen, we have a bogus "pending" restart->fn anyway,
this is harmless.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Pavel Emelyanov <xemul@sw.ru>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Toyo Abe <toyoa@mvista.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/compat.c

@@ -55,7 +55,6 @@ static long compat_nanosleep_restart(struct restart_block *restart)
 	set_fs(oldfs);
 
 	if (ret) {
-		restart->fn = compat_nanosleep_restart;
 		restart->arg1 = (unsigned long)rmtp;
 
 		if (rmtp && put_compat_timespec(&rmt, rmtp))

kernel/hrtimer.c

@@ -1340,8 +1340,6 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
 	struct hrtimer_sleeper t;
 	struct timespec __user  *rmtp;
 
-	restart->fn = do_no_restart_syscall;
-
 	hrtimer_init(&t.timer, restart->arg0, HRTIMER_MODE_ABS);
 	t.timer.expires.tv64 = ((u64)restart->arg3 << 32) | (u64) restart->arg2;
 
@@ -1355,8 +1353,6 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
 			return ret;
 	}
 
-	restart->fn = hrtimer_nanosleep_restart;
-
 	/* The other values in restart are already filled in */
 	return -ERESTART_RESTARTBLOCK;
 }