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Fix leak when returning BlockingIOError from a read - #143

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gvalkov merged 1 commit into
gvalkov:masterfrom
jbleon95:master
Nov 5, 2020
Merged

Fix leak when returning BlockingIOError from a read #143
gvalkov merged 1 commit into
gvalkov:masterfrom
jbleon95:master

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@jbleon95

@jbleon95 jbleon95 commented Oct 29, 2020

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Discovered a leak related to the read method for an InputDevice, when it returns a BlockingIOError while there is nothing to read. Ultimately tracked it down to a reference counting bug in device_read_many in input.c. Was able to recreate it using the following script

import evdev
import objgraph
import select
import time

def test_device_read_leak(device_name):
    device = evdev.InputDevice(device_name)
    start_time = time.time()

    while time.time() - start_time < 30:
        r, _, _ = select.select([device.fd], [], [], 0.1)
        try:
            for event in device.read():
                pass
        except BlockingIOError:
            pass

print("Before loop calling device.read() ~300 times")
objgraph.show_growth()
test_device_read_leak('/dev/input/event2')
print("\nAfter loop")
objgraph.show_growth()

Results before change

Before loop calling device.read() ~300 times
function                       3411     +3411
dict                           1616     +1616
tuple                          1371     +1371
wrapper_descriptor             1059     +1059
weakref                        1037     +1037
builtin_function_or_method      848      +848
method_descriptor               834      +834
getset_descriptor               614      +614
type                            467      +467
list                            380      +380

After loop
list      679      +299

After change

Before loop calling device.read() ~300 times
function                       3411     +3411
dict                           1616     +1616
tuple                          1371     +1371
wrapper_descriptor             1059     +1059
weakref                        1037     +1037
builtin_function_or_method      848      +848
method_descriptor               834      +834
getset_descriptor               614      +614
type                            467      +467
list                            380      +380

After loop

@gvalkov
gvalkov merged commit 00c0fa7 into gvalkov:master Nov 5, 2020
@gvalkov

gvalkov commented Nov 5, 2020

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Excellent. Thanks for the fix.

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2 participants

@jbleon95 @gvalkov