diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Kconfig.debug | 72 |
1 files changed, 41 insertions, 31 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 0dd1c04c732..8fee0a13ac5 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -848,59 +848,69 @@ config BUILD_DOCSRC Say N if you are unsure. config DYNAMIC_DEBUG - bool "Enable dynamic printk() call support" + bool "Enable dynamic printk() support" default n depends on PRINTK + depends on DEBUG_FS select PRINTK_DEBUG help Compiles debug level messages into the kernel, which would not otherwise be available at runtime. These messages can then be - enabled/disabled on a per module basis. This mechanism implicitly - enables all pr_debug() and dev_dbg() calls. The impact of this - compile option is a larger kernel text size of about 2%. + enabled/disabled based on various levels of scope - per source file, + function, module, format string, and line number. This mechanism + implicitly enables all pr_debug() and dev_dbg() calls. The impact of + this compile option is a larger kernel text size of about 2%. Usage: - Dynamic debugging is controlled by the debugfs file, - dynamic_printk/modules. This file contains a list of the modules that - can be enabled. The format of the file is the module name, followed - by a set of flags that can be enabled. The first flag is always the - 'enabled' flag. For example: + Dynamic debugging is controlled via the 'dynamic_debug/ddebug' file, + which is contained in the 'debugfs' filesystem. Thus, the debugfs + filesystem must first be mounted before making use of this feature. + We refer the control file as: <debugfs>/dynamic_debug/ddebug. This + file contains a list of the debug statements that can be enabled. The + format for each line of the file is: - <module_name> <enabled=0/1> - . - . - . + filename:lineno [module]function flags format - <module_name> : Name of the module in which the debug call resides - <enabled=0/1> : whether the messages are enabled or not + filename : source file of the debug statement + lineno : line number of the debug statement + module : module that contains the debug statement + function : function that contains the debug statement + flags : 'p' means the line is turned 'on' for printing + format : the format used for the debug statement From a live system: - snd_hda_intel enabled=0 - fixup enabled=0 - driver enabled=0 + nullarbor:~ # cat <debugfs>/dynamic_debug/ddebug + # filename:lineno [module]function flags format + fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" + fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" + fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" - Enable a module: + Example usage: - $echo "set enabled=1 <module_name>" > dynamic_printk/modules + // enable the message at line 1603 of file svcsock.c + nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > + <debugfs>/dynamic_debug/ddebug - Disable a module: + // enable all the messages in file svcsock.c + nullarbor:~ # echo -n 'file svcsock.c +p' > + <debugfs>/dynamic_debug/ddebug - $echo "set enabled=0 <module_name>" > dynamic_printk/modules + // enable all the messages in the NFS server module + nullarbor:~ # echo -n 'module nfsd +p' > + <debugfs>/dynamic_debug/ddebug - Enable all modules: + // enable all 12 messages in the function svc_process() + nullarbor:~ # echo -n 'func svc_process +p' > + <debugfs>/dynamic_debug/ddebug - $echo "set enabled=1 all" > dynamic_printk/modules + // disable all 12 messages in the function svc_process() + nullarbor:~ # echo -n 'func svc_process -p' > + <debugfs>/dynamic_debug/ddebug - Disable all modules: - - $echo "set enabled=0 all" > dynamic_printk/modules - - Finally, passing "dynamic_printk" at the command line enables - debugging for all modules. This mode can be turned off via the above - disable command. + See Documentation/dynamic-debug-howto.txt for additional information. source "samples/Kconfig" |