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Subject[PATCH 22/25] dynamic_debug: update Documentation/*, Kconfig.debug
Date
From: Jim Cromie <jim.cromie@gmail.com>

In dynamic-debug-howto.txt:

- add section: Debug Messages at Module Initialization Time
- update flags indicators in example outputs, from '-' to '=_'.
- make flags descriptions tabular
- add item on '_' flag-char
- add *.dyndbg, boot-args examples

In kernel-parameters.txt, add item on $modulename.dyndbg.

In Kconfig.debug, note that compiling with -DDEBUG enables all
pr_debug()s in that code.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
Documentation/dynamic-debug-howto.txt | 126 ++++++++++++++++++++++++--------
Documentation/kernel-parameters.txt | 9 +++
lib/Kconfig.debug | 17 +++--
3 files changed, 114 insertions(+), 38 deletions(-)

diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt
index 74e6c77..bba071d 100644
--- a/Documentation/dynamic-debug-howto.txt
+++ b/Documentation/dynamic-debug-howto.txt
@@ -2,7 +2,7 @@
Introduction
============

-This document describes how to use the dynamic debug (ddebug) feature.
+This document describes how to use the dynamic debug (dyndbg) feature.

Dynamic debug is designed to allow you to dynamically enable/disable kernel
code to obtain additional kernel information. Currently, if
@@ -49,10 +49,10 @@ via:

nullarbor:~ # cat <debugfs>/dynamic_debug/control
# filename:lineno [module]function flags format
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup - "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init - "\011max_inline : %d\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init - "\011sq_depth : %d\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init - "\011max_requests : %d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup =_ "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init =_ "\011max_inline : %d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init =_ "\011sq_depth : %d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init =_ "\011max_requests : %d\012"
...


@@ -65,12 +65,12 @@ nullarbor:~ # grep -i rdma <debugfs>/dynamic_debug/control | wc -l
nullarbor:~ # grep -i tcp <debugfs>/dynamic_debug/control | wc -l
42

-Note in particular that the third column shows the enabled behaviour
-flags for each debug statement callsite (see below for definitions of the
-flags). The default value, no extra behaviour enabled, is "-". So
-you can view all the debug statement callsites with any non-default flags:
+The third column shows the enabled behaviour flags for each debug
+statement callsite (see below for definitions of the flags). The
+default value, no extra behaviour enabled, is "=_". So you can view
+all the debug statement callsites with any non-default flags:

-nullarbor:~ # awk '$3 != "-"' <debugfs>/dynamic_debug/control
+nullarbor:~ # awk '$3 != "=_"' <debugfs>/dynamic_debug/control
# filename:lineno [module]function flags format
/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"

@@ -188,34 +188,27 @@ The flags specification comprises a change operation followed
by one or more flag characters. The change operation is one
of the characters:

--
- remove the given flags
-
-+
- add the given flags
-
-=
- set the flags to the given flags
+ - remove the given flags
+ + add the given flags
+ = set the flags to the given flags

The flags are:

-f
- Include the function name in the printed message
-l
- Include line number in the printed message
-m
- Include module name in the printed message
-p
- Causes a printk() message to be emitted to dmesg
-t
- Include thread ID in messages not generated from interrupt context
+ f Include the function name in the printed message
+ l Include line number in the printed message
+ m Include module name in the printed message
+ p Causes a printk() message to be emitted to dmesg
+ t Include thread ID in messages not generated from interrupt context
+ _ No flags are set. (Or'd with others on input)
+
+For display, the flags are preceded by '='
+(mnemonic: what the flags are currently equal to).

-Note the regexp ^[-+=][flmpt]+$ matches a flags specification.
-Note also that there is no convenient syntax to remove all
-the flags at once, you need to use "-flmpt".
+Note the regexp ^[-+=][flmpt_]+$ matches a flags specification.
+To clear all flags at once, use "=_" or "-flmpt".


-Debug messages during boot process
+Debug messages during Boot Process
==================================

To be able to activate debug messages during the boot process,
@@ -233,6 +226,56 @@ your machine (typically a laptop) has an Embedded Controller.
PCI (or other devices) initialization also is a hot candidate for using
this boot parameter for debugging purposes.

+Note: ddebug_query= works only on builtin modules, a more general
+approach follows.
+
+
+Debug Messages at Module Initialization Time
+============================================
+
+Enabling a module's debug messages via debug control file only works
+once the module is loaded; too late for callsites in init functions.
+And when module is unloaded, debug flag settings for the module are
+lost. Instead, a "dyndbg" module parameter can be passed:
+
+1. # the parameter can be used permanently via modprobe.conf(.local)
+ options module dyndbg=+pmflt
+ options module dyndbg # defaults to +p
+
+2. # added via kernel boot parameter: (this form works on built-ins too)
+ module.dyndbg=+mfp
+ module.dyndbg # defaults to +p
+
+3. # as an ordinary module parameter via modprobe
+ modprobe module dyndbg=+pmfl
+ modprobe module dyndbg # defaults to +p
+
+Dyndbg flags are applied in above order, with last having final say.
+This lets modprobe args supplement (dyndbg=+tfl) or override
+(dyndbg="=p_") previous settings.
+
+The $modname.dyndbg="value" must exclude "module $modname", as the
+$modname is taken from the param-name, and only 1 spec of each type is
+allowed.
+
+$module.dyndbg="..." on boot-line works on built-in modules as well as
+those loaded by modprobe (from either early or normal userspace), and
+overlaps debug_query functionality.
+
+
+*.dyndbg="+p" can be used to enable all debug callsites in builtin
+modules, or to set print-format defaults (="+mf") for those enabled
+separately. Loadable modules are not affected by wildcard rules, only
+$module.dyndbg boot options are applied to them.
+
+The dyndbg option is not implemented as an ordinary module parameter
+and thus will not show up in /sys/module/module_name/parameters/dyndbg
+
+Any settings given at boot-time (or by -DDEBUG flag during
+compilation) can be reverted later via the sysfs interface if the
+debug messages are no longer needed:
+
+ echo "module module_name -p" > <debugfs>/dynamic_debug/control

Examples
========
@@ -260,3 +303,22 @@ nullarbor:~ # echo -n 'func svc_process -p' >
// enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
nullarbor:~ # echo -n 'format "nfsd: READ" +p' >
<debugfs>/dynamic_debug/control
+
+// enable all messages
+nullarbor:~ # echo -n '+p' > <debugfs>/dynamic_debug/control
+
+// add module, function to all enabled messages
+nullarbor:~ # echo -n '+mf' > <debugfs>/dynamic_debug/control
+
+// boot-args example, with newlines and comments
+Kernel command line: ...
+ ddebug_query="func i2c_del_adapter +p; func tboot_probe +p"
+ dynamic_debug.verbose=1 // see whats going on
+ nouveau.dyndbg // implicit =+p
+ tsc_sync.dyndbg=+p // builtin on my kernel
+ i2c_core.dyndbg=+p // loaded by udev
+ *.dyndbg="+mf" // print module, func for enabled callsites
+ // in builtin modules
+ // multiple queries per module
+ k10temp.dyndbg="+p # comment in query is stripped "
+ pnp.dyndbg="func pnpacpi_get_resources +p; func pnp_assign_mem +p"
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 81c27b1..387443d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -691,6 +691,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.

dscc4.setup= [NET]

+ $modulename.dyndbg[=string]
+ [KNL,DYNAMIC_DEBUG] Enable debug messages in
+ $modulename for builtin or loadable modules. Debug
+ during module initialization is supported.
+ These parameters are not exposed in
+ /sys/module/${modnm}/parameters/dyndbg.
+ See Documentation/dynamic-debug-howto.txt for
+ details of allowed strings, etc.
+
earlycon= [KNL] Output early console device and options.
uart[8250],io,<addr>[,options]
uart[8250],mmio,<addr>[,options]
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 82928f5..0228b80 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1184,8 +1184,13 @@ config DYNAMIC_DEBUG
otherwise be available at runtime. These messages can then be
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%.
+ implicitly compiles in all pr_debug() and dev_dbg() calls, which
+ enlarges the kernel text size by about 2%.
+
+ If a source file is compiled with DEBUG flag set, any
+ pr_debug() calls in it are enabled by default, but can be
+ disabled at runtime as below. Note that DEBUG flag is
+ turned on by many CONFIG_*DEBUG* options.

Usage:

@@ -1202,16 +1207,16 @@ config DYNAMIC_DEBUG
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
+ flags : '=p' means the line is turned 'on' for printing
format : the format used for the debug statement

From a live system:

nullarbor:~ # cat <debugfs>/dynamic_debug/control
# 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"
+ 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"

Example usage:

--
1.7.7.3


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