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SubjectRe: [PATCH 2/3] ftrace: use struct pid
Date
Steven Rostedt <rostedt@goodmis.org> writes:

> From: Steven Rostedt <srostedt@redhat.com>
>
> Impact: clean up
>
> Eric Biederman suggested using the struct pid for filtering on
> pids in the kernel. This patch is based off of a demonstration
> of an implementation that Eric sent me in an email.

A little nit. I forgot to mention rcu_read_lock() is still needed in that
email.

> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
> ---
> kernel/trace/ftrace.c | 76 ++++++++++++++++++++++++++++--------------------
> kernel/trace/trace.h | 4 +-
> 2 files changed, 46 insertions(+), 34 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 57592a9..10b1d7c 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -48,7 +48,7 @@ int ftrace_enabled __read_mostly;
> static int last_ftrace_enabled;
>
> /* set when tracing only a pid */
> -int ftrace_pid_trace = -1;
> +struct pid *ftrace_pid_trace;
>
> /* Quick disabling of function tracer. */
> int function_trace_stop;
> @@ -153,7 +153,7 @@ static int __register_ftrace_function(struct ftrace_ops
> *ops)
> else
> func = ftrace_list_func;
>
> - if (ftrace_pid_trace >= 0) {
> + if (ftrace_pid_trace) {
> set_ftrace_pid_function(func);
> func = ftrace_pid_func;
> }
> @@ -209,7 +209,7 @@ 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 >= 0) {
> + if (ftrace_pid_trace) {
> set_ftrace_pid_function(func);
> func = ftrace_pid_func;
> }
> @@ -239,7 +239,7 @@ static void ftrace_update_pid_func(void)
>
> func = ftrace_trace_function;
>
> - if (ftrace_pid_trace >= 0) {
> + if (ftrace_pid_trace) {
> set_ftrace_pid_function(func);
> func = ftrace_pid_func;
> } else {
> @@ -1678,18 +1678,40 @@ ftrace_pid_read(struct file *file, char __user *ubuf,
> char buf[64];
> int r;
>
> - if (ftrace_pid_trace >= 0)
> - r = sprintf(buf, "%u\n", ftrace_pid_trace);
> + if (ftrace_pid_trace)
> + r = sprintf(buf, "%u\n", pid_nr(ftrace_pid_trace));
> else
> r = sprintf(buf, "no pid\n");
>
> return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
> }
>
> +static void clear_ftrace_pid_task(struct pid **pid)
> +{
> + struct task_struct *p;
> +
rcu_read_lock();

> + do_each_pid_task(*pid, PIDTYPE_PID, p) {
> + clear_tsk_trace_trace(p);
> + } while_each_pid_task(*pid, PIDTYPE_PID, p);
rcu_read_unlock()

> + put_pid(*pid);
> +
> + *pid = NULL;
> +}
> +
> +static void set_ftrace_pid_task(struct pid *pid)
> +{
> + struct task_struct *p;
> +
rcu_read_lock();
> + do_each_pid_task(pid, PIDTYPE_PID, p) {
> + set_tsk_trace_trace(p);
> + } while_each_pid_task(pid, PIDTYPE_PID, p);
rcu_read_unlock();
> +}
> +
> 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;
> @@ -1707,40 +1729,30 @@ ftrace_pid_write(struct file *filp, const char __user
> *ubuf,
> return ret;
>
> mutex_lock(&ftrace_start_lock);
> - if (ret < 0) {
> + if (val < 0) {
> /* disable pid tracing */
> - if (ftrace_pid_trace < 0)
> + if (!ftrace_pid_trace)
> goto out;
> - ftrace_pid_trace = -1;
> +
> + clear_ftrace_pid_task(&ftrace_pid_trace);
>
> } else {
> - struct task_struct *p;
> - int found = 0;
> + pid = find_get_pid(val);
>
> - if (ftrace_pid_trace == val)
> + if (pid == ftrace_pid_trace) {
> + put_pid(pid);
> goto out;
> -
> - /*
> - * Find the task that matches this pid.
> - * TODO: use pid namespaces instead.
> - */
> - rcu_read_lock();
> - for_each_process(p) {
> - if (p->pid == val) {
> - found = 1;
> - set_tsk_trace_trace(p);
> - } else if (test_tsk_trace_trace(p))
> - clear_tsk_trace_trace(p);
> }
> - rcu_read_unlock();
>
> - if (found)
> - ftrace_pid_trace = val;
> - else {
> - if (ftrace_pid_trace < 0)
> - goto out;
> - ftrace_pid_trace = -1;
> - }
> + 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);
> }
>
> /* update the function call */
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 95fff37..8b81b4d 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -541,11 +541,11 @@ print_graph_function(struct trace_iterator *iter)
> }
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> -extern int ftrace_pid_trace;
> +extern struct pid *ftrace_pid_trace;
>
> static inline int ftrace_trace_task(struct task_struct *task)
> {
> - if (ftrace_pid_trace < 0)
> + if (ftrace_pid_trace)
> return 1;
>
> return test_tsk_trace_trace(task);
> --
> 1.5.6.5
>
> --


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