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tracing: Create set_event_notrace_pid to not trace tasks

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There's currently a way to select a task that should only have its events
traced, but there's no way to select a task not to have itsevents traced.
Add a set_event_notrace_pid file that acts the same as set_event_pid (and is
also affected by event-fork), but the task pids in this file will not be
traced even if they are listed in the set_event_pid file. This makes it easy
for tools like trace-cmd to "hide" itself from beint traced by events when
it is recording other tasks.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware)
2020-03-25 19:51:19 -04:00
parent b3b1e6eded
commit 2768362603
3 changed files with 244 additions and 72 deletions
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11
kernel/trace/ftrace.c
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@@ -6987,11 +6987,6 @@ void ftrace_pid_follow_fork(struct trace_array *tr, bool enable)
}
}
enum {
TRACE_PIDS = BIT(0),
TRACE_NO_PIDS = BIT(1),
};
static void clear_ftrace_pids(struct trace_array *tr, int type)
{
struct trace_pid_list *pid_list;
@@ -7004,13 +6999,11 @@ static void clear_ftrace_pids(struct trace_array *tr, int type)
lockdep_is_held(&ftrace_lock));
/* Make sure there's something to do */
if (!(((type & TRACE_PIDS) && pid_list) ||
((type & TRACE_NO_PIDS) && no_pid_list)))
if (!pid_type_enabled(type, pid_list, no_pid_list))
return;
/* See if the pids still need to be checked after this */
if (!((!(type & TRACE_PIDS) && pid_list) ||
(!(type & TRACE_NO_PIDS) && no_pid_list))) {
if (!still_need_pid_events(type, pid_list, no_pid_list)) {
unregister_trace_sched_switch(ftrace_filter_pid_sched_switch_probe, tr);
for_each_possible_cpu(cpu)
per_cpu_ptr(tr->array_buffer.data, cpu)->ftrace_ignore_pid = FTRACE_PID_TRACE;