[ltt-dev] PATCH] Make lttcrl/lttd show error when channel not exist

[Zhaolei]

Hello, Mathieu

When run lttctl with a no-exist debugfs's channel dir,
it don't report error:
  # lttctl -n channel1 -d -l /no_exist -t /tmp/channel1
  Linux Trace Toolkit Trace Control 0.54-10102008
  
  Controlling trace : channel1
  
  Linux Trace Toolkit Trace Daemon 0.54-10102008
  
  Reading from debugfs directory : /no_exist/channel1
  Writing to trace directory : /tmp/channel1

  #

It is because lttd don't return error in daemon mode:
  # lttd -d -t /tmp/channel1 -c /no_exist
  Linux Trace Toolkit Trace Daemon 0.54-10102008
  
  Reading from debugfs directory : /no_exist
  Writing to trace directory : /tmp/channel1
  
  # echo $?
  0
  #

I moved daemon() after channels_init() and make it seems fixed.
I tested patched program and haven't found problem:
  # lttctl -n channel1 -d -l /no_exist -t /tmp/channel1
  Linux Trace Toolkit Trace Control 0.54-10102008

  Controlling trace : channel1

  Linux Trace Toolkit Trace Daemon 0.54-10102008

  Reading from debugfs directory : /no_exist/channel1
  Writing to trace directory : /tmp/channel1

  /no_exist/channel1: No such file or directory
  Trace start error
  #
  #
  # lttd -d -t /tmp/channel1 -c /no_exist
  Linux Trace Toolkit Trace Daemon 0.54-10102008

  Reading from debugfs directory : /no_exist
  Writing to trace directory : /tmp/channel1
  
  /no_exist: No such file or directory
  #
  #
  # lttctl -n channel1 -d -l /mnt/debugfs/ltt/ -t /tmp/channel1
  Linux Trace Toolkit Trace Control 0.54-10102008

  Controlling trace : channel1

  Linux Trace Toolkit Trace Daemon 0.54-10102008

  Reading from debugfs directory : /mnt/debugfs/ltt//channel1
  Writing to trace directory : /tmp/channel1

  Creating trace subdirectory /tmp/channel1
  Adding inotify for channel /mnt/debugfs/ltt//channel1/
  Added inotify for channel /mnt/debugfs/ltt//channel1/, wd 1
  Channel file : /mnt/debugfs/ltt//channel1/cpu_0
  Opening file.
  Channel file : /mnt/debugfs/ltt//channel1/control
  Entering channel subdirectory...
  Creating trace subdirectory /tmp/channel1/control
  Adding inotify for channel /mnt/debugfs/ltt//channel1/control/
  Added inotify for channel /mnt/debugfs/ltt//channel1/control/, wd 2
  Channel file : /mnt/debugfs/ltt//channel1/control/network_0
  Opening file.
  Channel file : /mnt/debugfs/ltt//channel1/control/modules_0
  Opening file.
  Channel file : /mnt/debugfs/ltt//channel1/control/processes_0
  Opening file.
  Channel file : /mnt/debugfs/ltt//channel1/control/interrupts_0
  Opening file.
  Channel file : /mnt/debugfs/ltt//channel1/control/metadata_0
  Opening file.
  #

Cound you review it?

Btw, this patch will make lttctl and lttv show more detail message, is it necessary to cut them?

Signed-off-by: Zhao Lei <zhaolei at cn.fujitsu.com>
---
diff -Nur ltt-control-0.54-10102008.org/lttd/lttd.c ltt-control-0.54-10102008/lttd/lttd.c
--- ltt-control-0.54-10102008.org/lttd/lttd.c	2008-10-15 15:29:54.000000000 +0800
+++ ltt-control-0.54-10102008/lttd/lttd.c	2008-10-21 13:15:06.000000000 +0800
@@ -911,15 +911,6 @@
 
 	show_info();
 
-	if(daemon_mode) {
-		ret = daemon(0, 0);
-		
-		if(ret == -1) {
-			perror("An error occured while daemonizing.");
-			exit(-1);
-		}
-	}
-
 	/* Connect the signal handlers */
 	act.sa_handler = handler;
 	act.sa_flags = 0;
@@ -934,6 +925,15 @@
 	if(ret = channels_init())
 		return ret;
 
+	if(daemon_mode) {
+		ret = daemon(0, 0);
+
+		if(ret == -1) {
+			perror("An error occured while daemonizing.");
+			exit(-1);
+		}
+	}
+
 	tids = malloc(sizeof(pthread_t) * num_threads);
 	for(i=0; i<num_threads; i++) {