| ======================= |
| Logging to a RAM Buffer |
| ======================= |
| |
| .. warning:: |
| Migrated from: |
| https://cwiki.apache.org/confluence/display/NUTTX/Logging+to+a+RAM+Buffer |
| |
| |
| Default Debug Output |
| ==================== |
| |
| By default, when you enable debug output, that output goes to the system |
| console and is mixed up with the normal console output. Normally, that is |
| sufficient. However there are some cases where you might want to do things |
| differently. For example, if there is time critical debug output that |
| interferes with the operation of the device. Or, if you would like to |
| separate the normal console output from the debug output. |
| |
| One particularly troublesome case is network debug output to console in a |
| Telnet session. Since the telnet session remaps the console output to the |
| Telnet connection, the network debug output can generate infinite loops |
| because the network operation generates debug output to the console, which |
| generates more debug output, ... and on and on. |
| |
| With some creative configuration of the NuttX SYStem LOGging (SYSLOG) feature, |
| these problems can all be eliminated. |
| |
| The syslog Device |
| ================= |
| |
| Debug output goes to the `syslog` device. As mentioned above, the default syslog |
| device device is the system console. However there are many options to control |
| the behavior of the syslog – too many in fact. There are so many options that |
| you will probably have to perform experiments to get the syslog working as you |
| would like it too. |
| |
| The RAMLOG Device |
| ================= |
| |
| The RAMLOG device is a special character device that can really be used for |
| most any purpose. However, the RAMLOG device has some special attributes |
| that make it ideal for use as a syslogging device. |
| |
| * It supports the ``syslog_write`` interface needed for system logging |
| * It behaves much like a pipe: It implements a queue. Writing to the RAMLOG |
| device adds data to the head of the queue; reading from the RAMLOG device |
| removes data from the tail of the queue. |
| * It can be configured to return EOF when you try to read and there is |
| nothing available in the RAMLOG. |
| |
| |
| Using the RAMLOG as the syslog Device |
| ===================================== |
| |
| This Wiki page addresses the setup for one configuration: Using a `RAMLOG` as |
| the syslog device. A RAMLOG is a circular buffer in memory. In this |
| configuration, all debugout output goes to this circular buffer and can later |
| be retrieved using the NSH ``dmesg`` command |
| |
| Here is the summary of what I had to do to get the RAMLOG working as the |
| syslog device. I use a simulation configuration, but for this feature this |
| does not matter. |
| |
| .. code-block:: bash |
| |
| tools/configure.sh sim:nsh |
| make menuconfig |
| |
| I added the following settings. First, these just give me some debug output |
| to test against: |
| |
| .. code-block:: c |
| |
| CONFIG_DEBUG=y |
| CONFIG_DEBUG_FS=y |
| CONFIG_DEBUG_SCHED=y |
| |
| This configures the virtual file system to support the syslog device and is a |
| necessary pre-condition for other settings: |
| |
| .. code-block:: c |
| |
| CONFIG_SYSLOG=y |
| |
| These enables the RAMLOG and configure it for use as the syslog device |
| |
| .. code-block:: c |
| |
| CONFIG_RAMLOG=y |
| CONFIG_RAMLOG_CONSOLE_BUFSIZE=8192 |
| CONFIG_RAMLOG_NONBLOCKING=y |
| CONFIG_RAMLOG_SYSLOG=y |
| #CONFIG_SYSLOG_CHAR undefined, else duplicate output with syslog_write() |
| |
| Now when I run NuttX, I get output like this. The ``dmesg`` command now appears |
| as an NSH command: |
| |
| .. code-block:: bash |
| |
| NuttShell (NSH) NuttX-7.1 |
| nsh> help |
| help usage: help [-v] [<cmd>] |
| [ dd free mkdir mw sleep |
| ? df help mkfatfs ps test |
| break dmesg hexdump mkfifo pwd true |
| cat echo kill mkrd rm umount |
| cd exec losetup mh rmdir unset |
| cp exit ls mount set usleep |
| cmp false mb mv sh xd |
| Builtin Apps: |
| hello |
| |
| The ``dmesg`` command dumps the contents and clears the RAMLOG: |
| |
| .. code-block:: bash |
| |
| nsh> dmesg |
| nx_start: Entry |
| up_unblock_task: Unblocking TCB=52bc70 |
| up_unblock_task: New Active Task TCB=52bc70 |
| posix_spawn_exec: ERROR: exec failed: 22 |
| cmd_mkrd: RAMDISK at 52d4f0 |
| posix_spawn_exec: ERROR: exec failed: 22 |
| mkfatfs_tryfat16: Too few or too many clusters for FAT16: 4081 < 983 < 1022 |
| mkfatfs_clustersearch: Cannot format FAT16 at 1 sectors/cluster |
| mkfatfs_configfatfs: Sector size: 512 bytes |
| mkfatfs_configfatfs: Number of sectors: 1024 sectors |
| mkfatfs_configfatfs: FAT size: 12 bits |
| mkfatfs_configfatfs: Number FATs: 2 |
| mkfatfs_configfatfs: Sectors per cluster: 1 sectors |
| mkfatfs_configfatfs: FS size: 3 sectors |
| mkfatfs_configfatfs: 985 clusters |
| mkfatfs_configfatfs: Root directory slots: 512 |
| mkfatfs_configfatfs: Volume ID: 00000000 |
| mkfatfs_configfatfs: Volume Label: " " |
| posix_spawn_exec: ERROR: exec failed: 22 |
| fat_mount: FAT12: |
| fat_mount: HW sector size: 512 |
| fat_mount: sectors: 1024 |
| fat_mount: FAT reserved: 1 |
| fat_mount: sectors: 1024 |
| fat_mount: start sector: 1 |
| fat_mount: root sector: 7 |
| fat_mount: root entries: 512 |
| fat_mount: data sector: 39 |
| fat_mount: FSINFO sector: 0 |
| fat_mount: Num FATs: 2 |
| fat_mount: FAT sectors: 3 |
| fat_mount: sectors/cluster: 1 |
| fat_mount: max clusters: 985 |
| fat_mount: FSI free count -1 |
| fat_mount: next free 0 |
| posix_spawn_exec: ERROR: exec failed: 22 |
| posix_spawn_exec: ERROR: exec failed: 22 |
| nsh> |
| |
| As mentioned, the dmesg command clears the RAMLOG. So when it is used again, |
| only new debug output is shown: |
| |
| .. code-block:: bash |
| |
| nsh> dmesg |
| posix_spawn_exec: ERROR: exec failed: 22 |
| |
| As a side note, the ``posix_spawn_exec`` error will occur on each command in |
| this configuration. That is because NSH first tries to execute a command from |
| a file found in the file system on the ``PATH`` variable. You will not see |
| this error in your system unless you have ``CONFIG_NSH_FILE_APPS=y`` |
| defined in your configuration. |
