Trouble porting my code to caio about caio HOT 23 CLOSED

I've got the same problem when using aiofile.

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I think It's fixed in caio==0.6.0

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aiofile 3.0.0 requires caio~=0.5.3, but you'll have caio 0.6.0 which is incompatible.

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Oh. My bad

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@honglei aiofile==3.1.0 has been released.

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@honglei actually you should use Linux kernel >=4.18 it's was not a bug that's was the fixes avoiding compatibility issue. io_submit system call supports all required features since Linux 4.18.

The thread-based implementation will be used otherwise.

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My kernel is 4.4.15 and I cannot update it, when using fsync , it raised "Bad file descriptor" Error.

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@mosquito I think caio should choose to use theaded-mode if it cannot work correctly before linux kernel 4.18

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@honglei that's will happen transparently for you. When caio importing selects preferred implementation.

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@mosquito But under Linux 4.4.15/Python3.8/caio 0.60, caio.preferred is caio.linux_aio

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@mosquito But under Linux 4.4.15/Python3.8/caio 0.60, caio.preferred is caio.linux_aio

@honglei Please provide uname -r output.

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4.4.15-deepin-wutip-421-inspur-monitor-native-debugless

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>>> os.uname()
posix.uname_result(sysname='Linux', nodename='lccy6', release='4.4.15-deepin-wutip-421-inspur-monitor-native-debugless', version='#298 SMP Mon Jun 29 14:14:12 CST 2020', machine='sw_64')

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Hi! I am running Linux 5.8.3 and just updated to caio 0.6.0, still the same thing 😕

$ uname -a
Linux genesis 5.8.3-arch1-1 #1 SMP PREEMPT Fri, 21 Aug 2020 16:54:16 +0000 x86_64 GNU/Linux

$ python -c 'import caio; print(caio.__version__)'
0.6.0

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@FFY00 @honglei Thanks for your persistence, it's really my bug. I found a solution and soon will release it.

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Maybe this way:

import os
if os.name =='posix':
    os_version = os.uname().release.split("-")[0]
    version = tuple( [int(i) for i in os_version.split(".")])
    if version<(4,18):
        print("thread_aio")
    else:
        print("linux_aio")

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@honglei actually something like this but on c. Anyway, 0.6.1 has been released. I will happy if you try to check this out.

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Unfortunately this still doesn't fix my issue. My kernel is very recent, do you have any idea why this might not be working?

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@FFY00 it's happening when the kernel is not able to perform the asynchronous operation with this file. I found a problem with fsync/fdsync operations on old kernels, and avoid this. I guess that's isn't the last issue with old kernels, but when you bring some details e.g. environment, kernel version Linux distro, etc. I might reproduce this on VM, I guess, and try to resolve it, or restrict libaio based implementation for this kernel as a bad case.

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@FFY00 So after fast reading the documentation about UHID I found out this:

Non-blocking operations are supported by setting O_NONBLOCK.

Probably you do not need use caio for this (I guess kernel is not able to handle this file descriptor) try something like this:

import os, asyncio, fcntl

f = open(...)

rv = fcntl.fcntl(f, fcntl.F_SETFL, os.O_NONBLOCK)


def ready_to_read(fp):
    pass


def ready_to_write(fp):
    pass


loop = asyncio.get_event_loop()
loop.add_reader(f.fileno(), ready_to_read, f)
loop.add_writer(f.fileno(), ready_to_write, f)

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Still linux_aio under kernel 4.4.15

lccy@lccy6:/opt/python38/bin$ ./python3
Python 3.8.4rc1 (default, Jul  1 2020, 11:44:28)
[GCC 5.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import caio
<frozen importlib._bootstrap>:219: RuntimeWarning: Linux supports fsync/fdsync with io_submit since 4.18 but current kernel 4.4.15-deepin-wutip-421-inspur-monitor-native-debugless doesn't support it. Related calls will have no effect.
>>> caio.preferred
<module 'caio.linux_aio' from '/opt/python38/lib/python3.8/site-packages/caio/linux_aio.cpython-38.so'>
>>> caio.__version__
'0.6.1'
>>> os.uname()
posix.uname_result(sysname='Linux', nodename='lccy6', release='4.4.15-deepin-wutip-421-inspur-monitor-native-debugless', version='#298 SMP Mon Jun 29 14:14:12 CST 2020', machine='sw_64')

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@mosquito I think the last modification only give a warning, but have no effect for caio.preferred selection.

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@honglei please see Troubleshooting part in README.rst

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