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tracing: Introduce saved_cmdlines_size file

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Introduce saved_cmdlines_size file for changing the number of saved pid-comms.
saved_cmdlines currently stores 128 command names using SAVED_CMDLINES, but
'no-existing processes' names are often lost in saved_cmdlines when we
read the trace data. So, by introducing saved_cmdlines_size file, we can
now change the 128 command names saved to something much larger if needed.

When we write a value to saved_cmdlines_size, the number of the value will
be stored in pid-comm list:

	# echo 1024 > /sys/kernel/debug/tracing/saved_cmdlines_size

Here, 1024 command names can be stored. The default number is 128 and the maximum
number is PID_MAX_DEFAULT (=32768 if CONFIG_BASE_SMALL is not set). So, if we
want to avoid losing any command names, we need to set 32768 to
saved_cmdlines_size.

We can read the maximum number of the list:

	# cat /sys/kernel/debug/tracing/saved_cmdlines_size
	128

Link: http://lkml.kernel.org/p/20140605012427.22115.16173.stgit@yunodevel

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Yoshihiro YUNOMAE 2014-06-05 10:24:27 +09:00 committed by Steven Rostedt
parent beba4bb096
commit 939c7a4f04
1 changed files with 154 additions and 24 deletions
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178
kernel/trace/trace.c
View File

@ -1285,22 +1285,71 @@ void tracing_reset_all_online_cpus(void)
}
}
#define SAVED_CMDLINES 128
#define SAVED_CMDLINES_DEFAULT 128
#define NO_CMDLINE_MAP UINT_MAX
static unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
static unsigned map_cmdline_to_pid[SAVED_CMDLINES];
static char saved_cmdlines[SAVED_CMDLINES][TASK_COMM_LEN];
static int cmdline_idx;
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
struct saved_cmdlines_buffer {
unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
unsigned *map_cmdline_to_pid;
unsigned cmdline_num;
int cmdline_idx;
char *saved_cmdlines;
};
static struct saved_cmdlines_buffer *savedcmd;
/* temporary disable recording */
static atomic_t trace_record_cmdline_disabled __read_mostly;
static void trace_init_cmdlines(void)
static inline char *get_saved_cmdlines(int idx)
{
memset(&map_pid_to_cmdline, NO_CMDLINE_MAP, sizeof(map_pid_to_cmdline));
memset(&map_cmdline_to_pid, NO_CMDLINE_MAP, sizeof(map_cmdline_to_pid));
cmdline_idx = 0;
return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
}
static inline void set_cmdline(int idx, const char *cmdline)
{
memcpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
}
static int allocate_cmdlines_buffer(unsigned int val,
struct saved_cmdlines_buffer *s)
{
s->map_cmdline_to_pid = kmalloc(val * sizeof(*s->map_cmdline_to_pid),
GFP_KERNEL);
if (!s->map_cmdline_to_pid)
return -ENOMEM;
s->saved_cmdlines = kmalloc(val * TASK_COMM_LEN, GFP_KERNEL);
if (!s->saved_cmdlines) {
kfree(s->map_cmdline_to_pid);
return -ENOMEM;
}
s->cmdline_idx = 0;
s->cmdline_num = val;
memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
sizeof(s->map_pid_to_cmdline));
memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
val * sizeof(*s->map_cmdline_to_pid));
return 0;
}
static int trace_create_savedcmd(void)
{
int ret;
savedcmd = kmalloc(sizeof(struct saved_cmdlines_buffer), GFP_KERNEL);
if (!savedcmd)
return -ENOMEM;
ret = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT, savedcmd);
if (ret < 0) {
kfree(savedcmd);
savedcmd = NULL;
return -ENOMEM;
}
return 0;
}
int is_tracing_stopped(void)
@ -1457,9 +1506,9 @@ static int trace_save_cmdline(struct task_struct *tsk)
if (!arch_spin_trylock(&trace_cmdline_lock))
return 0;
idx = map_pid_to_cmdline[tsk->pid];
idx = savedcmd->map_pid_to_cmdline[tsk->pid];
if (idx == NO_CMDLINE_MAP) {
idx = (cmdline_idx + 1) % SAVED_CMDLINES;
idx = (savedcmd->cmdline_idx + 1) % savedcmd->cmdline_num;
/*
* Check whether the cmdline buffer at idx has a pid
@ -1467,17 +1516,17 @@ static int trace_save_cmdline(struct task_struct *tsk)
* need to clear the map_pid_to_cmdline. Otherwise we
* would read the new comm for the old pid.
*/
pid = map_cmdline_to_pid[idx];
pid = savedcmd->map_cmdline_to_pid[idx];
if (pid != NO_CMDLINE_MAP)
map_pid_to_cmdline[pid] = NO_CMDLINE_MAP;
savedcmd->map_pid_to_cmdline[pid] = NO_CMDLINE_MAP;
map_cmdline_to_pid[idx] = tsk->pid;
map_pid_to_cmdline[tsk->pid] = idx;
savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
savedcmd->map_pid_to_cmdline[tsk->pid] = idx;
cmdline_idx = idx;
savedcmd->cmdline_idx = idx;
}
memcpy(&saved_cmdlines[idx], tsk->comm, TASK_COMM_LEN);
set_cmdline(idx, tsk->comm);
arch_spin_unlock(&trace_cmdline_lock);
@ -1503,9 +1552,9 @@ static void __trace_find_cmdline(int pid, char comm[])
return;
}
map = map_pid_to_cmdline[pid];
map = savedcmd->map_pid_to_cmdline[pid];
if (map != NO_CMDLINE_MAP)
strcpy(comm, saved_cmdlines[map]);
strcpy(comm, get_saved_cmdlines(map));
else
strcpy(comm, "<...>");
}
@ -3593,6 +3642,7 @@ static const char readme_msg[] =
" trace_options\t\t- Set format or modify how tracing happens\n"
"\t\t\t Disable an option by adding a suffix 'no' to the\n"
"\t\t\t option name\n"
" saved_cmdlines_size\t- echo command number in here to store comm-pid list\n"
#ifdef CONFIG_DYNAMIC_FTRACE
"\n available_filter_functions - list of functions that can be filtered on\n"
" set_ftrace_filter\t- echo function name in here to only trace these\n"
@ -3715,7 +3765,8 @@ static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
(*pos)++;
for (; ptr < &map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) {
for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
ptr++) {
if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
continue;
@ -3733,7 +3784,7 @@ static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
preempt_disable();
arch_spin_lock(&trace_cmdline_lock);
v = &map_cmdline_to_pid[0];
v = &savedcmd->map_cmdline_to_pid[0];
while (l <= *pos) {
v = saved_cmdlines_next(m, v, &l);
if (!v)
@ -3781,6 +3832,79 @@ static const struct file_operations tracing_saved_cmdlines_fops = {
.release = seq_release,
};
static ssize_t
tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char buf[64];
int r;
arch_spin_lock(&trace_cmdline_lock);
r = sprintf(buf, "%u\n", savedcmd->cmdline_num);
arch_spin_unlock(&trace_cmdline_lock);
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}
static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
{
kfree(s->saved_cmdlines);
kfree(s->map_cmdline_to_pid);
kfree(s);
}
static int tracing_resize_saved_cmdlines(unsigned int val)
{
struct saved_cmdlines_buffer *s, *savedcmd_temp;
s = kmalloc(sizeof(struct saved_cmdlines_buffer), GFP_KERNEL);
if (!s)
return -ENOMEM;
if (allocate_cmdlines_buffer(val, s) < 0) {
kfree(s);
return -ENOMEM;
}
arch_spin_lock(&trace_cmdline_lock);
savedcmd_temp = savedcmd;
savedcmd = s;
arch_spin_unlock(&trace_cmdline_lock);
free_saved_cmdlines_buffer(savedcmd_temp);
return 0;
}
static ssize_t
tracing_saved_cmdlines_size_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
unsigned long val;
int ret;
ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
if (ret)
return ret;
/* must have at least 1 entry or less than PID_MAX_DEFAULT */
if (!val || val > PID_MAX_DEFAULT)
return -EINVAL;
ret = tracing_resize_saved_cmdlines((unsigned int)val);
if (ret < 0)
return ret;
*ppos += cnt;
return cnt;
}
static const struct file_operations tracing_saved_cmdlines_size_fops = {
.open = tracing_open_generic,
.read = tracing_saved_cmdlines_size_read,
.write = tracing_saved_cmdlines_size_write,
};
static ssize_t
tracing_set_trace_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
@ -6375,6 +6499,9 @@ static __init int tracer_init_debugfs(void)
trace_create_file("saved_cmdlines", 0444, d_tracer,
NULL, &tracing_saved_cmdlines_fops);
trace_create_file("saved_cmdlines_size", 0644, d_tracer,
NULL, &tracing_saved_cmdlines_size_fops);
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
@ -6611,18 +6738,19 @@ __init static int tracer_alloc_buffers(void)
if (!temp_buffer)
goto out_free_cpumask;
if (trace_create_savedcmd() < 0)
goto out_free_temp_buffer;
/* TODO: make the number of buffers hot pluggable with CPUS */
if (allocate_trace_buffers(&global_trace, ring_buf_size) < 0) {
printk(KERN_ERR "tracer: failed to allocate ring buffer!\n");
WARN_ON(1);
goto out_free_temp_buffer;
goto out_free_savedcmd;
}
if (global_trace.buffer_disabled)
tracing_off();
trace_init_cmdlines();
if (trace_boot_clock) {
ret = tracing_set_clock(&global_trace, trace_boot_clock);
if (ret < 0)
@ -6668,6 +6796,8 @@ __init static int tracer_alloc_buffers(void)
return 0;
out_free_savedcmd:
free_saved_cmdlines_buffer(savedcmd);
out_free_temp_buffer:
ring_buffer_free(temp_buffer);
out_free_cpumask: