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Fix race condition in signal handling

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This commit is contained in:
Marcin Kulik
2016-06-27 12:25:59 +02:00
parent 08e7a6f1ce
commit 1c915e45ba
1 changed files with 29 additions and 7 deletions
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36
asciinema/pty_recorder.py
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@@ -10,6 +10,7 @@ import select
import io
import shlex
import sys
import struct
from .stdout import Stdout
@@ -59,17 +60,20 @@ class PtyRecorder(object):
_write_master(data)
def _copy():
def _copy(signal_fd):
'''Main select loop.
Passes control to _master_read() or _stdin_read()
when new data arrives.
'''
fds = [master_fd, pty.STDIN_FILENO]
fds = [master_fd, pty.STDIN_FILENO, signal_fd]
while True:
rfds, wfds, xfds = select.select(fds, [], [])
try:
rfds, wfds, xfds = select.select(fds, [], [])
except InterruptedError as e:
continue
if master_fd in rfds:
data = os.read(master_fd, 1024)
@@ -85,13 +89,31 @@ class PtyRecorder(object):
else:
_handle_stdin_read(data)
if signal_fd in rfds:
data = os.read(signal_fd, 1024)
if data:
signals = struct.unpack('%uB' % len(data), data)
for sig in signals:
if sig == signal.SIGCHLD:
os.close(master_fd)
return
elif sig == signal.SIGWINCH:
_set_pty_size()
pid, master_fd = pty.fork()
if pid == pty.CHILD:
os.execlp(command[0], *command)
old_sigwinch_handler = signal.signal(signal.SIGWINCH, lambda signal, frame: _set_pty_size())
old_sigchld_handler = signal.signal(signal.SIGCHLD, lambda signal, frame: os.close(master_fd))
pipe_r, pipe_w = os.pipe()
flags = fcntl.fcntl(pipe_w, fcntl.F_GETFL, 0)
flags = flags | os.O_NONBLOCK
flags = fcntl.fcntl(pipe_w, fcntl.F_SETFL, flags)
signal.set_wakeup_fd(pipe_w)
old_sigwinch_handler = signal.signal(signal.SIGWINCH, lambda signal, frame: None)
old_sigchld_handler = signal.signal(signal.SIGCHLD, lambda signal, frame: None)
try:
mode = tty.tcgetattr(pty.STDIN_FILENO)
@@ -103,8 +125,8 @@ class PtyRecorder(object):
_set_pty_size()
try:
_copy()
except (IOError, OSError):
_copy(pipe_r)
finally:
if restore:
tty.tcsetattr(pty.STDIN_FILENO, tty.TCSAFLUSH, mode)