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Commit e32d8956 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: add ability to only trace swapper tasks 



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: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 978f3a45

kernel/trace/ftrace.c

+63 −11
Original line number Diff line number Diff line
@@ -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;



	do_each_pid_task(*pid, PIDTYPE_PID, p) {

	get_online_cpus();

	for_each_online_cpu(cpu) {

		p = idle_task(cpu);

		clear_tsk_trace_trace(p);

	} while_each_pid_task(*pid, PIDTYPE_PID, p);

	put_pid(*pid);

	}

	put_online_cpus();

}



	*pid = NULL;

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 set_ftrace_pid_task(struct pid *pid)

static void clear_ftrace_pid(struct pid *pid)

{

	struct task_struct *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);

}



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);