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Date: Fri, 20 Feb 2009 17:58:48 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Andy Whitcroft <apw@...onical.com>, Ingo Molnar <mingo@...e.hu>,
Steven Rostedt <rostedt@...dmis.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/function-graph-tracer: make set_graph_function
file support ftrace regex
On Thu, Feb 19, 2009 at 09:13:12PM +0100, Frederic Weisbecker wrote:
> Impact: trace only functions matching a pattern
>
> The set_graph_function file let one to trace only one or several
> chosen functions and follow all their code flow.
>
> Currently, only a constant function name is allowed so this patch
> allows the ftrace_regex functions:
>
> _ matches all functions that end with "name":
> echo *name > set_graph_function
>
> _ matches all functions that begin with "name":
> echo name* > set_graph_function
>
> _ matches all functions that contains "name":
> echo *name* > set_graph_function
>
> Example:
>
> echo mutex* > set_graph_function
>
> 0) | mutex_lock_nested() {
> 0) 0.563 us | __might_sleep();
> 0) 2.072 us | }
> 0) | mutex_unlock() {
> 0) 1.036 us | __mutex_unlock_slowpath();
> 0) 2.433 us | }
> 0) | mutex_unlock() {
> 0) 0.691 us | __mutex_unlock_slowpath();
> 0) 1.787 us | }
> 0) | mutex_lock_interruptible_nested() {
> 0) 0.548 us | __might_sleep();
> 0) 1.945 us | }
>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
> kernel/trace/ftrace.c | 56 +++++++++++++++++++++++++++++++++---------------
> 1 files changed, 38 insertions(+), 18 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 7dd5a2b..cf59f4c 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1895,6 +1895,10 @@ static void *g_start(struct seq_file *m, loff_t *pos)
>
> mutex_lock(&graph_lock);
>
> + /* Nothing, tell g_show to print all functions are enabled */
> + if (!ftrace_graph_count && !*pos)
> + return (void *)1;
> +
> p = g_next(m, p, pos);
>
> return p;
> @@ -1913,6 +1917,11 @@ static int g_show(struct seq_file *m, void *v)
> if (!ptr)
> return 0;
>
> + if (ptr == (unsigned long *)1) {
> + seq_printf(m, "#### all functions enabled ####\n");
> + return 0;
> + }
> +
> kallsyms_lookup(*ptr, NULL, NULL, NULL, str);
>
> seq_printf(m, "%s\n", str);
> @@ -1966,38 +1975,51 @@ ftrace_graph_read(struct file *file, char __user *ubuf,
> }
>
> static int
> -ftrace_set_func(unsigned long *array, int idx, char *buffer)
> +ftrace_set_func(unsigned long *array, int *idx, char *buffer)
> {
> - char str[KSYM_SYMBOL_LEN];
> struct dyn_ftrace *rec;
> struct ftrace_page *pg;
> + int search_len;
> int found = 0;
> - int j;
> + int type, not;
> + char *search;
> + bool exists;
> + int i;
>
> if (ftrace_disabled)
> return -ENODEV;
>
> + /* decode regex */
> + type = ftrace_setup_glob(buffer, strlen(buffer), &search, ¬);
> + if (not)
> + return -EINVAL;
> +
> + search_len = strlen(search);
> +
> mutex_lock(&ftrace_lock);
> do_for_each_ftrace_rec(pg, rec) {
>
> + if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
> + break;
> +
> if (rec->flags & (FTRACE_FL_FAILED | FTRACE_FL_FREE))
> continue;
>
> - kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
> - if (strcmp(str, buffer) == 0) {
> - /* Return 1 if we add it to the array */
> - found = 1;
> - for (j = 0; j < idx; j++)
> - if (array[j] == rec->ip) {
> - found = 0;
> + if (ftrace_match_record(rec, search, search_len, type)) {
> + /* ensure it is not already in the array */
> + exists = false;
> + for (i = 0; i < *idx; i++)
> + if (array[i] == rec->ip) {
> + exists = true;
> break;
> }
> - if (found)
> - array[idx] = rec->ip;
> - goto out;
> + if (!exists) {
> + array[(*idx)++] = rec->ip;
> + found = 1;
> + }
> }
> } while_for_each_ftrace_rec();
> - out:
> +
> mutex_unlock(&ftrace_lock);
>
> return found ? 0 : -EINVAL;
> @@ -2066,13 +2088,11 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
> }
> buffer[index] = 0;
>
> - /* we allow only one at a time */
> - ret = ftrace_set_func(array, ftrace_graph_count, buffer);
> + /* we allow only one expression at a time */
> + ret = ftrace_set_func(array, &ftrace_graph_count, buffer);
> if (ret)
> goto out;
>
> - ftrace_graph_count++;
> -
> file->f_pos += read;
>
> ret = read;
> --
> 1.6.1
>
>
BTW, I got something that looked like a false positive with checkpatch.pl on this patch:
ERROR: return is not a function, parentheses are not required
#56: FILE: kernel/trace/ftrace.c:1900:
+ return (void *)1;
total: 1 errors, 0 warnings, 101 lines checked
0001-tracing-function-graph-tracer-make-set_graph_functi.patch has style problems, please review. If any of these
errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
It is confusing a cast with a function call.
--
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