dynamic_debug: process multiple debug-queries on a line

Insert ddebug_exec_queries() in place of ddebug_exec_query().  It
splits the query string on [;\n], and calls ddebug_exec_query() on
each.  All queries are processed independent of errors, allowing a
query to fail, for example when a module is not installed.  Empty
lines and comments are skipped.  Errors are counted, and the last
error seen (negative) or the number of callsites found (0 or positive)
is returned.  Return code checks are altered accordingly.

With this, multiple queries can be given in ddebug_query, allowing
more selective enabling of callsites.  As a side effect, a set of
commands can be batched in:

	cat cmd-file > $DBGMT/dynamic_debug/control

We dont want a ddebug_query syntax error to kill the dynamic debug
facility, so dynamic_debug_init() zeros ddebug_exec_queries()'s return
code after logging the appropriate message, so that ddebug tables are
preserved and $DBGMT/dynamic_debug/control file is created.  This
would be appropriate even without accepting multiple queries.

This patch also alters ddebug_change() to return number of callsites
matched (which typically is the same as number of callsites changed).
ddebug_exec_query() also returns the number found, or a negative value
if theres a parse error on the query.

Splitting on [;\n] prevents their use in format-specs, but selecting
callsites on punctuation is brittle anyway, meaningful and selective
substrings are more typical.

Note: splitting queries on ';' before handling trailing #comments
means that a ';' also terminates a comment, and text after the ';' is
treated as another query.  This trailing query will almost certainly
result in a parse error and thus have no effect other than the error
message.  The double corner case with unexpected results is:

     ddebug_query="func foo +p # enable foo ; +p"

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 15 deletions

diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt
index 378b5d1bf436..74e6c7782678 100644
--- a/Documentation/dynamic-debug-howto.txt
+++ b/Documentation/dynamic-debug-howto.txt
@@ -12,7 +12,7 @@ dynamically enabled per-callsite.
 Dynamic debug has even more useful features:
 
  * Simple query language allows turning on and off debugging statements by
-   matching any combination of:
+   matching any combination of 0 or 1 of:
 
    - source filename
    - function name
@@ -79,31 +79,24 @@ Command Language Reference
 ==========================
 
 At the lexical level, a command comprises a sequence of words separated
-by whitespace characters.  Note that newlines are treated as word
-separators and do *not* end a command or allow multiple commands to
-be done together.  So these are all equivalent:
+by spaces or tabs.  So these are all equivalent:
 
 nullarbor:~ # echo -c 'file svcsock.c line 1603 +p' >
                                 <debugfs>/dynamic_debug/control
 nullarbor:~ # echo -c '  file   svcsock.c     line  1603 +p  ' >
                                 <debugfs>/dynamic_debug/control
-nullarbor:~ # echo -c 'file svcsock.c\nline 1603 +p' >
-                                <debugfs>/dynamic_debug/control
 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
                                 <debugfs>/dynamic_debug/control
 
-Commands are bounded by a write() system call.  If you want to do
-multiple commands you need to do a separate "echo" for each, like:
+Command submissions are bounded by a write() system call.
+Multiple commands can be written together, separated by ';' or '\n'.
 
-nullarbor:~ # echo 'file svcsock.c line 1603 +p' > /proc/dprintk ;\
-> echo 'file svcsock.c line 1563 +p' > /proc/dprintk
+  ~# echo "func pnpacpi_get_resources +p; func pnp_assign_mem +p" \
+     > <debugfs>/dynamic_debug/control
 
-or even like:
+If your query set is big, you can batch them too:
 
-nullarbor:~ # (
-> echo 'file svcsock.c line 1603 +p' ;\
-> echo 'file svcsock.c line 1563 +p' ;\
-> ) > /proc/dprintk
+  ~# cat query-batch-file > <debugfs>/dynamic_debug/control
 
 At the syntactical level, a command comprises a sequence of match
 specifications, followed by a flags change specification.