tracing: Check all tasks on each CPU when filtering pids
My tests found that if a task is running but not filtered when set_event_pid
is modified, then it can still be traced.
Call on_each_cpu() to check if the current running task should be filtered
and update the per cpu flags of tr->data appropriately.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ab07058..2b7fccd 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1549,6 +1549,22 @@
return (PAGE_SIZE << pid_list->order) / sizeof(pid_t);
}
+static void ignore_task_cpu(void *data)
+{
+ struct trace_array *tr = data;
+ struct trace_pid_list *pid_list;
+
+ /*
+ * This function is called by on_each_cpu() while the
+ * event_mutex is held.
+ */
+ pid_list = rcu_dereference_protected(tr->filtered_pids,
+ mutex_is_locked(&event_mutex));
+
+ this_cpu_write(tr->trace_buffer.data->ignore_pid,
+ check_ignore_pid(pid_list, current));
+}
+
static ssize_t
ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
@@ -1711,6 +1727,12 @@
tr, INT_MAX);
register_trace_prio_sched_wakeup(event_filter_pid_sched_wakeup_probe_post,
tr, 0);
+
+ /*
+ * Ignoring of pids is done at task switch. But we have to
+ * check for those tasks that are currently running.
+ */
+ on_each_cpu(ignore_task_cpu, tr, 1);
}
mutex_unlock(&event_mutex);