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Code Issues Releases Wiki Activity

connection: Make ConnectionBase.cancel() more robust

Browse Source 
Check with poll() if the command is already finished first, to avoid
sending SIGKILL to unrelated processes due to PID recycling.

The race window still exists between the call to poll() and _cancel(),
but is reduced a great deal.
This commit is contained in:
douglas-raillard-arm 2021-03-23 11:15:35 +00:00 committed by Marc Bonnici
parent 31f7c1e8f9
commit 6cabad14d0
1 changed files with 12 additions and 4 deletions
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16
devlib/connection.py
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@ -105,12 +105,20 @@ class BackgroundCommand(ABC):
"""
self.send_signal(signal.SIGKILL)
@abstractmethod
def cancel(self, kill_timeout=_KILL_TIMEOUT):
"""
Try to gracefully terminate the process by sending ``SIGTERM``, then
waiting for ``kill_timeout`` to send ``SIGKILL``.
"""
if self.poll() is None:
self._cancel(kill_timeout=kill_timeout)
@abstractmethod
def _cancel(self, kill_timeout):
"""
Method to override in subclasses to implement :meth:`cancel`.
"""
pass
@abstractmethod
def wait(self):
@ -209,7 +217,7 @@ class PopenBackgroundCommand(BackgroundCommand):
def poll(self):
return self.popen.poll()
def cancel(self, kill_timeout=_KILL_TIMEOUT):
def _cancel(self, kill_timeout):
popen = self.popen
os.killpg(os.getpgid(popen.pid), signal.SIGTERM)
try:
@ -266,7 +274,7 @@ class ParamikoBackgroundCommand(BackgroundCommand):
else:
return None
def cancel(self, kill_timeout=_KILL_TIMEOUT):
def _cancel(self, kill_timeout):
self.send_signal(signal.SIGTERM)
# Check if the command terminated quickly
time.sleep(10e-3)
@ -340,7 +348,7 @@ class AdbBackgroundCommand(BackgroundCommand):
def poll(self):
return self.adb_popen.poll()
def cancel(self, kill_timeout=_KILL_TIMEOUT):
def _cancel(self, kill_timeout):
self.send_signal(signal.SIGTERM)
try:
self.adb_popen.wait(timeout=_KILL_TIMEOUT)