uprobes: Do not setup ->active_uprobe/state prematurely

handle_swbp() sets utask->active_uprobe before handler_chain(),
and UTASK_SSTEP before pre_ssout(). This complicates the code
for no reason,  arch_ hooks or consumer->handler() should not
(and can't) use this info.

Change handle_swbp() to initialize them after pre_ssout(), and
remove the no longer needed cleanup-utask code.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
cked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

kernel/events/uprobes.c

@@ -1496,22 +1496,19 @@ static void handle_swbp(struct pt_regs *regs)
 		if (!utask)
 			goto cleanup_ret;
 	}
-	utask->active_uprobe = uprobe;
+
 	handler_chain(uprobe, regs);
 	if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
 		goto cleanup_ret;
 
-	utask->state = UTASK_SSTEP;
 	if (!pre_ssout(uprobe, regs, bp_vaddr)) {
 		arch_uprobe_enable_step(&uprobe->arch);
+		utask->active_uprobe = uprobe;
+		utask->state = UTASK_SSTEP;
 		return;
 	}
 
 cleanup_ret:
-	if (utask) {
-		utask->active_uprobe = NULL;
-		utask->state = UTASK_RUNNING;
-	}
 	if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
 
 		/*