Some filesystem tests are failing when their image is prepared with guestmount, but succeeding if loop mounts are used instead. The reason seems to be a race condition the guestmount(1) manual page explains:
When guestunmount(1)/fusermount(1) exits, guestmount may still be running and cleaning up the mountpoint. The disk image will not be fully finalized.
This means that scripts like the following have a nasty race condition:
guestmount -a disk.img -i /mnt # copy things into /mnt guestunmount /mnt # immediately try to use 'disk.img' ** UNSAFE **
The solution is to use the --pid-file option to write the guestmount PID to a file, then after guestunmount spin waiting for this PID to exit.
The Python standard library has an os.waitpid() function for waiting a child to terminate, but it cannot wait on non-child processes. Implement a utility function that can do this by polling the process repeatedly for a given duration, optionally killing the process if it won't terminate on its own. Apply the suggested solution with this utility function, which makes the failing tests succeed again.
Signed-off-by: Alper Nebi Yasak alpernebiyasak@gmail.com ---
test/py/tests/test_fs/conftest.py | 13 ++++++++++- test/py/u_boot_utils.py | 36 +++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+), 1 deletion(-)
diff --git a/test/py/tests/test_fs/conftest.py b/test/py/tests/test_fs/conftest.py index e3c461635f8e..6b1ff05a8143 100644 --- a/test/py/tests/test_fs/conftest.py +++ b/test/py/tests/test_fs/conftest.py @@ -8,6 +8,7 @@ import re from subprocess import call, check_call, check_output, CalledProcessError from fstest_defs import * +import u_boot_utils as util
supported_fs_basic = ['fat16', 'fat32', 'ext4'] supported_fs_ext = ['fat16', 'fat32'] @@ -206,7 +207,7 @@ def mount_fs(fs_type, device, mount_point): global fuse_mounted
try: - check_call('guestmount -a %s -m /dev/sda %s' + check_call('guestmount --pid-file guestmount.pid -a %s -m /dev/sda %s' % (device, mount_point), shell=True) fuse_mounted = True return @@ -235,6 +236,16 @@ def umount_fs(mount_point): if fuse_mounted: call('sync') call('guestunmount %s' % mount_point, shell=True) + + try: + with open("guestmount.pid", "r") as pidfile: + pid = int(pidfile.read()) + util.waitpid(pid, kill=True) + os.remove("guestmount.pid") + + except FileNotFoundError: + pass + else: call('sudo umount %s' % mount_point, shell=True)
diff --git a/test/py/u_boot_utils.py b/test/py/u_boot_utils.py index 939d82eec12a..e816c7fbb6a3 100644 --- a/test/py/u_boot_utils.py +++ b/test/py/u_boot_utils.py @@ -8,6 +8,7 @@ import os import os.path import pytest +import signal import sys import time import re @@ -339,3 +340,38 @@ def crc32(u_boot_console, address, count): assert m, 'CRC32 operation failed.'
return m.group(1) + +def waitpid(pid, timeout=60, kill=False): + """Wait a process to terminate by its PID + + This is an alternative to a os.waitpid(pid, 0) call that works on + processes that aren't children of the python process. + + Args: + pid: PID of a running process. + timeout: Time in seconds to wait. + kill: Whether to forcibly kill the process after timeout. + + Returns: + True, if the process ended on its own. + False, if the process was killed by this function. + + Raises: + TimeoutError, if the process is still running after timeout. + """ + try: + for _ in range(timeout): + os.kill(pid, 0) + time.sleep(1) + + if kill: + os.kill(pid, signal.SIGKILL) + return False + + except ProcessLookupError: + return True + + raise TimeoutError( + "Process with PID {} did not terminate after {} seconds." + .format(pid, timeout) + )