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tracing: Support multiple pids in set_pid_ftrace file
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Adding the possibility to set more than 1 pid in the set_pid_ftrace
file, thus allowing to trace more than 1 independent processes.

Usage:

 sh-4.0# echo 284 > ./set_ftrace_pid
 sh-4.0# cat ./set_ftrace_pid
 284
 sh-4.0# echo 1 >> ./set_ftrace_pid
 sh-4.0# echo 0 >> ./set_ftrace_pid
 sh-4.0# cat ./set_ftrace_pid
 swapper tasks
 1
 284
 sh-4.0# echo 4 > ./set_ftrace_pid
 sh-4.0# cat ./set_ftrace_pid
 4
 sh-4.0# echo > ./set_ftrace_pid
 sh-4.0# cat ./set_ftrace_pid
 no pid
 sh-4.0#

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091013203425.565454612@goodmis.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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jolsa@redhat.com authored and Ingo Molnar committed Oct 14, 2009
1 parent 194ec34 commit 756d17e
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Showing 2 changed files with 167 additions and 71 deletions.
234 changes: 165 additions & 69 deletions kernel/trace/ftrace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,13 @@ static int last_ftrace_enabled;
/* Quick disabling of function tracer. */
int function_trace_stop;

/* List for set_ftrace_pid's pids. */
LIST_HEAD(ftrace_pids);
struct ftrace_pid {
struct list_head list;
struct pid *pid;
};

/*
* ftrace_disabled is set when an anomaly is discovered.
* ftrace_disabled is much stronger than ftrace_enabled.
Expand Down Expand Up @@ -159,7 +166,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
else
func = ftrace_list_func;

if (ftrace_pid_trace) {
if (!list_empty(&ftrace_pids)) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
}
Expand Down Expand Up @@ -207,7 +214,7 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
if (ftrace_list->next == &ftrace_list_end) {
ftrace_func_t func = ftrace_list->func;

if (ftrace_pid_trace) {
if (!list_empty(&ftrace_pids)) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
}
Expand Down Expand Up @@ -235,7 +242,7 @@ static void ftrace_update_pid_func(void)
func = __ftrace_trace_function;
#endif

if (ftrace_pid_trace) {
if (!list_empty(&ftrace_pids)) {
set_ftrace_pid_function(func);
func = ftrace_pid_func;
} else {
Expand Down Expand Up @@ -825,8 +832,6 @@ static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
}
#endif /* CONFIG_FUNCTION_PROFILER */

/* set when tracing only a pid */
struct pid *ftrace_pid_trace;
static struct pid * const ftrace_swapper_pid = &init_struct_pid;

#ifdef CONFIG_DYNAMIC_FTRACE
Expand Down Expand Up @@ -2758,23 +2763,6 @@ static inline void ftrace_startup_enable(int command) { }
# define ftrace_shutdown_sysctl() do { } while (0)
#endif /* CONFIG_DYNAMIC_FTRACE */

static ssize_t
ftrace_pid_read(struct file *file, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char buf[64];
int r;

if (ftrace_pid_trace == ftrace_swapper_pid)
r = sprintf(buf, "swapper tasks\n");
else if (ftrace_pid_trace)
r = sprintf(buf, "%u\n", pid_vnr(ftrace_pid_trace));
else
r = sprintf(buf, "no pid\n");

return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}

static void clear_ftrace_swapper(void)
{
struct task_struct *p;
Expand Down Expand Up @@ -2825,14 +2813,12 @@ static void set_ftrace_pid(struct pid *pid)
rcu_read_unlock();
}

static void clear_ftrace_pid_task(struct pid **pid)
static void clear_ftrace_pid_task(struct pid *pid)
{
if (*pid == ftrace_swapper_pid)
if (pid == ftrace_swapper_pid)
clear_ftrace_swapper();
else
clear_ftrace_pid(*pid);

*pid = NULL;
clear_ftrace_pid(pid);
}

static void set_ftrace_pid_task(struct pid *pid)
Expand All @@ -2843,11 +2829,140 @@ static void set_ftrace_pid_task(struct pid *pid)
set_ftrace_pid(pid);
}

static int ftrace_pid_add(int p)
{
struct pid *pid;
struct ftrace_pid *fpid;
int ret = -EINVAL;

mutex_lock(&ftrace_lock);

if (!p)
pid = ftrace_swapper_pid;
else
pid = find_get_pid(p);

if (!pid)
goto out;

ret = 0;

list_for_each_entry(fpid, &ftrace_pids, list)
if (fpid->pid == pid)
goto out_put;

ret = -ENOMEM;

fpid = kmalloc(sizeof(*fpid), GFP_KERNEL);
if (!fpid)
goto out_put;

list_add(&fpid->list, &ftrace_pids);
fpid->pid = pid;

set_ftrace_pid_task(pid);

ftrace_update_pid_func();
ftrace_startup_enable(0);

mutex_unlock(&ftrace_lock);
return 0;

out_put:
if (pid != ftrace_swapper_pid)
put_pid(pid);

out:
mutex_unlock(&ftrace_lock);
return ret;
}

static void ftrace_pid_reset(void)
{
struct ftrace_pid *fpid, *safe;

mutex_lock(&ftrace_lock);
list_for_each_entry_safe(fpid, safe, &ftrace_pids, list) {
struct pid *pid = fpid->pid;

clear_ftrace_pid_task(pid);

list_del(&fpid->list);
kfree(fpid);
}

ftrace_update_pid_func();
ftrace_startup_enable(0);

mutex_unlock(&ftrace_lock);
}

static void *fpid_start(struct seq_file *m, loff_t *pos)
{
mutex_lock(&ftrace_lock);

if (list_empty(&ftrace_pids) && (!*pos))
return (void *) 1;

return seq_list_start(&ftrace_pids, *pos);
}

static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
{
if (v == (void *)1)
return NULL;

return seq_list_next(v, &ftrace_pids, pos);
}

static void fpid_stop(struct seq_file *m, void *p)
{
mutex_unlock(&ftrace_lock);
}

static int fpid_show(struct seq_file *m, void *v)
{
const struct ftrace_pid *fpid = list_entry(v, struct ftrace_pid, list);

if (v == (void *)1) {
seq_printf(m, "no pid\n");
return 0;
}

if (fpid->pid == ftrace_swapper_pid)
seq_printf(m, "swapper tasks\n");
else
seq_printf(m, "%u\n", pid_vnr(fpid->pid));

return 0;
}

static const struct seq_operations ftrace_pid_sops = {
.start = fpid_start,
.next = fpid_next,
.stop = fpid_stop,
.show = fpid_show,
};

static int
ftrace_pid_open(struct inode *inode, struct file *file)
{
int ret = 0;

if ((file->f_mode & FMODE_WRITE) &&
(file->f_flags & O_TRUNC))
ftrace_pid_reset();

if (file->f_mode & FMODE_READ)
ret = seq_open(file, &ftrace_pid_sops);

return ret;
}

static ssize_t
ftrace_pid_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
struct pid *pid;
char buf[64];
long val;
int ret;
Expand All @@ -2860,57 +2975,38 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,

buf[cnt] = 0;

/*
* Allow "echo > set_ftrace_pid" or "echo -n '' > set_ftrace_pid"
* to clean the filter quietly.
*/
strstrip(buf);
if (strlen(buf) == 0)
return 1;

ret = strict_strtol(buf, 10, &val);
if (ret < 0)
return ret;

mutex_lock(&ftrace_lock);
if (val < 0) {
/* disable pid tracing */
if (!ftrace_pid_trace)
goto out;

clear_ftrace_pid_task(&ftrace_pid_trace);

} else {
/* swapper task is special */
if (!val) {
pid = ftrace_swapper_pid;
if (pid == ftrace_pid_trace)
goto out;
} else {
pid = find_get_pid(val);

if (pid == ftrace_pid_trace) {
put_pid(pid);
goto out;
}
}

if (ftrace_pid_trace)
clear_ftrace_pid_task(&ftrace_pid_trace);

if (!pid)
goto out;

ftrace_pid_trace = pid;

set_ftrace_pid_task(ftrace_pid_trace);
}
ret = ftrace_pid_add(val);

/* update the function call */
ftrace_update_pid_func();
ftrace_startup_enable(0);
return ret ? ret : cnt;
}

out:
mutex_unlock(&ftrace_lock);
static int
ftrace_pid_release(struct inode *inode, struct file *file)
{
if (file->f_mode & FMODE_READ)
seq_release(inode, file);

return cnt;
return 0;
}

static const struct file_operations ftrace_pid_fops = {
.read = ftrace_pid_read,
.write = ftrace_pid_write,
.open = ftrace_pid_open,
.write = ftrace_pid_write,
.read = seq_read,
.llseek = seq_lseek,
.release = ftrace_pid_release,
};

static __init int ftrace_init_debugfs(void)
Expand Down
4 changes: 2 additions & 2 deletions kernel/trace/trace.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -496,12 +496,12 @@ print_graph_function(struct trace_iterator *iter)
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

extern struct pid *ftrace_pid_trace;
extern struct list_head ftrace_pids;

#ifdef CONFIG_FUNCTION_TRACER
static inline int ftrace_trace_task(struct task_struct *task)
{
if (!ftrace_pid_trace)
if (list_empty(&ftrace_pids))
return 1;

return test_tsk_trace_trace(task);
Expand Down

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