ftrace: Fix trace_add_event_call() to initialize list

Handle failure path in trace_add_event_call() to fix the below bug
which occurred when I tried to add invalid event twice.

Could not create debugfs 'kmalloc' directory
Failed to register kprobe event: kmalloc
Faild to register probe event(-1)
------------[ cut here ]------------
WARNING: at /home/mhiramat/ksrc/random-tracing/lib/list_debug.c:26
__list_add+0x27/0x5c()
Hardware name:
list_add corruption. next->prev should be prev (c07d78cc), but was
00001000. (next=d854236c).
Modules linked in: sunrpc uinput virtio_net virtio_balloon i2c_piix4 pcspkr
i2c_core virtio_blk virtio_pci virtio_ring virtio [last unloaded:
scsi_wait_scan]
Pid: 1394, comm: tee Not tainted 2.6.31-rc9 #51
Call Trace:
 [<c0438424>] warn_slowpath_common+0x65/0x7c
 [<c05371b3>] ? __list_add+0x27/0x5c
 [<c043846f>] warn_slowpath_fmt+0x24/0x27
 [<c05371b3>] __list_add+0x27/0x5c
 [<c047f050>] list_add+0xa/0xc
 [<c047f8f5>] trace_add_event_call+0x60/0x97
 [<c0483133>] command_trace_probe+0x42c/0x51b
 [<c044a1b3>] ? remove_wait_queue+0x22/0x27
 [<c042a9c0>] ? __wake_up+0x32/0x3b
 [<c04832f6>] probes_write+0xd4/0x10a
 [<c0483222>] ? probes_write+0x0/0x10a
 [<c04b27a9>] vfs_write+0x80/0xdf
 [<c04b289c>] sys_write+0x3b/0x5d
 [<c0670d41>] syscall_call+0x7/0xb
---[ end trace 2b962b5dc1fdc07d ]---

Signed-off-by: Masami Hiramatsu <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Frank Ch. Eigler <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: K.Prasad <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Cc: Tom Zanussi <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

Author: Masami Hiramatsu

kernel/trace/trace_events.c

@@ -1010,9 +1010,12 @@ static int __trace_add_event_call(struct ftrace_event_call *call)
 		return -ENOENT;
 
 	list_add(&call->list, &ftrace_events);
-	return event_create_dir(call, d_events, &ftrace_event_id_fops,
+	ret = event_create_dir(call, d_events, &ftrace_event_id_fops,
 				&ftrace_enable_fops, &ftrace_event_filter_fops,
 				&ftrace_event_format_fops);
+	if (ret < 0)
+		list_del(&call->list);
+	return ret;
 }
 
 /* Add an additional event_call dynamically */