Python script for gdb, uses procfs to monitor task state then stores timestamp and backtrace to file

trace_task.py

import pathlib, re, time

line_pattern = re.compile(r'(.*?):\s+(.*)')

'''
	Example usage, note that MODULE is this file and is in the directory you run gdb from
	Note that gdb needs root privs


	# gdb /bin/subl3 -p $(pidof subl3)
	pi
	>>> import sys
	>>> sys.path.append('.')
	>>> import MODULE as A
	>>> A.experiment('this_file_will_be_overwritten.txt')

'''


def wait_for_task_state(proc_id, task_id, target_state, polling_interval=0.01):
	task_dir = pathlib.Path(f'/proc/{proc_id}/task')
	while True:
		info = dict(match.groups() for match in line_pattern.finditer((task_dir / f'{task_id}/status').read_text()))
		if info['State'][0] == target_state:
			break
		time.sleep(polling_interval)

def info_file_to_dict(path):
	return dict(match.groups() for match in line_pattern.finditer((path).read_text()))

def find_task(proc_id, task_name):
	task_dir = pathlib.Path(f'/proc/{proc_id}/task')
	for task in task_dir.iterdir():
		info = info_file_to_dict(task / 'status')
		if info['Name'] == task_name:
			return task.name

def enumerate_pid_matching_name(proc_name):
	results = list()
	for proc in pathlib.Path(f'/proc').iterdir():
		if proc.name.isdigit():
			info = info_file_to_dict(proc / 'status')
			if info['Name'] == proc_name:
				results.append(proc.name)
	return results

def get_backtrace(frame):
	result = list()
	while frame:
		result.append(frame)
		frame = frame.older()
	return result


def experiment(target_file):
	import signal, gdb, threading

	s3pid, = enumerate_pid_matching_name('subl3')
	s3tid = find_task(s3pid, 'subl3')

	def wait():
		wait_for_task_state(s3pid, s3tid, 'R')
		signal.raise_signal(signal.SIGINT)

	gdb.execute("set pagination off")	#This prevents things to stop when there is long output since gdb will output a summary automatically
	#Of course this hook could be modified to not do that but pagination off is probably still a good idea

	with open(target_file, 'w') as outfile:
		while True:

			threading.Thread(target=wait).start()
			gdb.execute('c')

			bt = get_backtrace(gdb.newest_frame())
			print(time.time(), ' → '.join(f'{f.name() or "??"}[0x{f.pc():x}]' for f in bt), file=outfile, flush=True)