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ftrace: add ability to only trace swapper tasks

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Impact: new feature

This patch lets the swapper tasks of all CPUS be filtered by the
set_ftrace_pid file.

If '0' is echoed into this file, then all the idle tasks (aka swapper)
is flagged to be traced.  This affects all CPU idle tasks.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-12-04 00:26:41 -05:00 committed by Ingo Molnar
parent 978f3a45d9
commit e32d895691
1 changed files with 64 additions and 12 deletions
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68
kernel/trace/ftrace.c
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@ -49,6 +49,7 @@ static int last_ftrace_enabled;
/* set when tracing only a pid */
struct pid *ftrace_pid_trace;
static struct pid * const ftrace_swapper_pid = (struct pid *)1;
/* Quick disabling of function tracer. */
int function_trace_stop;
@ -1678,7 +1679,9 @@ ftrace_pid_read(struct file *file, char __user *ubuf,
char buf[64];
int r;
if (ftrace_pid_trace)
if (ftrace_pid_trace == ftrace_swapper_pid)
r = sprintf(buf, "swapper tasks\n");
else if (ftrace_pid_trace)
r = sprintf(buf, "%u\n", pid_nr(ftrace_pid_trace));
else
r = sprintf(buf, "no pid\n");
@ -1686,19 +1689,43 @@ ftrace_pid_read(struct file *file, char __user *ubuf,
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}
static void clear_ftrace_pid_task(struct pid **pid)
static void clear_ftrace_swapper(void)
{
struct task_struct *p;
int cpu;
get_online_cpus();
for_each_online_cpu(cpu) {
p = idle_task(cpu);
clear_tsk_trace_trace(p);
}
put_online_cpus();
}
static void set_ftrace_swapper(void)
{
struct task_struct *p;
int cpu;
get_online_cpus();
for_each_online_cpu(cpu) {
p = idle_task(cpu);
set_tsk_trace_trace(p);
}
put_online_cpus();
}
static void clear_ftrace_pid(struct pid *pid)
{
struct task_struct *p;
do_each_pid_task(*pid, PIDTYPE_PID, p) {
do_each_pid_task(pid, PIDTYPE_PID, p) {
clear_tsk_trace_trace(p);
} while_each_pid_task(*pid, PIDTYPE_PID, p);
put_pid(*pid);
*pid = NULL;
} while_each_pid_task(pid, PIDTYPE_PID, p);
put_pid(pid);
}
static void set_ftrace_pid_task(struct pid *pid)
static void set_ftrace_pid(struct pid *pid)
{
struct task_struct *p;
@ -1707,6 +1734,24 @@ static void set_ftrace_pid_task(struct pid *pid)
} while_each_pid_task(pid, PIDTYPE_PID, p);
}
static void clear_ftrace_pid_task(struct pid **pid)
{
if (*pid == ftrace_swapper_pid)
clear_ftrace_swapper();
else
clear_ftrace_pid(*pid);
*pid = NULL;
}
static void set_ftrace_pid_task(struct pid *pid)
{
if (pid == ftrace_swapper_pid)
set_ftrace_swapper();
else
set_ftrace_pid(pid);
}
static ssize_t
ftrace_pid_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
@ -1736,6 +1781,12 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
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);
@ -1743,6 +1794,7 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
put_pid(pid);
goto out;
}
}
if (ftrace_pid_trace)
clear_ftrace_pid_task(&ftrace_pid_trace);