Commit 42584c81 authored by Yoshihiro YUNOMAE's avatar Yoshihiro YUNOMAE Committed by Steven Rostedt

tracing: Have saved_cmdlines use the seq_read infrastructure

Current tracing_saved_cmdlines_read() implementation is naive; It allocates
a large buffer, constructs output data to that buffer for each read
operation, and then copies a portion of the buffer to the user space
buffer. This has several issues such as slow memory allocation, high
CPU usage, and even corruption of the output data.

The seq_read infrastructure is made to handle this type of work.
By converting it to use seq_read() the code becomes smaller, simplified,
as well as correct.

Link: http://lkml.kernel.org/p/20140220084431.3839.51793.stgit@yunodevelSigned-off-by: default avatarHidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarYoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 81dc9f0e
......@@ -3699,55 +3699,74 @@ static const struct file_operations tracing_readme_fops = {
.llseek = generic_file_llseek,
};
static ssize_t
tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,
size_t cnt, loff_t *ppos)
static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
{
char *buf_comm;
char *file_buf;
char *buf;
int len = 0;
int pid;
int i;
unsigned int *ptr = v;
file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);
if (!file_buf)
return -ENOMEM;
if (*pos || m->count)
ptr++;
buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);
if (!buf_comm) {
kfree(file_buf);
return -ENOMEM;
}
(*pos)++;
buf = file_buf;
for (; ptr < &map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) {
if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
continue;
for (i = 0; i < SAVED_CMDLINES; i++) {
int r;
return ptr;
}
pid = map_cmdline_to_pid[i];
if (pid == -1 || pid == NO_CMDLINE_MAP)
continue;
return NULL;
}
trace_find_cmdline(pid, buf_comm);
r = sprintf(buf, "%d %s\n", pid, buf_comm);
buf += r;
len += r;
static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
{
void *v;
loff_t l = 0;
v = &map_cmdline_to_pid[0];
while (l <= *pos) {
v = saved_cmdlines_next(m, v, &l);
if (!v)
return NULL;
}
len = simple_read_from_buffer(ubuf, cnt, ppos,
file_buf, len);
return v;
}
static void saved_cmdlines_stop(struct seq_file *m, void *v)
{
}
kfree(file_buf);
kfree(buf_comm);
static int saved_cmdlines_show(struct seq_file *m, void *v)
{
char buf[TASK_COMM_LEN];
unsigned int *pid = v;
return len;
trace_find_cmdline(*pid, buf);
seq_printf(m, "%d %s\n", *pid, buf);
return 0;
}
static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
.start = saved_cmdlines_start,
.next = saved_cmdlines_next,
.stop = saved_cmdlines_stop,
.show = saved_cmdlines_show,
};
static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
{
if (tracing_disabled)
return -ENODEV;
return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
}
static const struct file_operations tracing_saved_cmdlines_fops = {
.open = tracing_open_generic,
.read = tracing_saved_cmdlines_read,
.llseek = generic_file_llseek,
.open = tracing_saved_cmdlines_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
static ssize_t
......
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