>From: Gregory Nutt <spudan...@gmail.com>
>Sent: 03 March 2023 19:03
>To: dev@nuttx.apache.org
>Subject: Re: Help me understand file open/close behaviours?
>
>On 3/3/2023 12:56 PM, Gregory Nutt wrote:
>> On 3/3/2023 12:36 PM, Nathan Hartman wrote:
>>> On Fri, Mar 3, 2023 at 1:07 PM Tim Hardisty <t...@hardisty.co.uk> wrote:
>>>> The bug I thought I had in a driver I'm developing (well, one of
>>>> them!) appears to be related to file closing.
>>>>
>>>> - I have a related example-type app I'm using to exercise and check
>>>> the driver. It opens 2 "files" (O-RDONLY) to read data from the
>>>> device driver
>>>> - I have enabled CONFIG_SIGKILL_ACTION to allow me to ctrl-c from
>>>> the console if the app is misbehaving or, I thought, just to exit it.
>>>>
>>>> The behaviours I see are:
>>>>
>>>> 1) If I ctrl-c, the open files are not closed and if I re-run the
>>>> app, the system crashes. It is the very first printf statement of
>>>> the app that causes the crash, at the point the printf routine calls
>>>> lib_fflush (not looked further yet).
>>>> 2) If I ensure the test app reads console input too, and map a
>>>> character received character (e.g. 'x') to a clean exit, I can then
>>>> re-run the app without issue.
>>>>
>>>> I don't think I saw this behaviour with the previous driver I did,
>>>> so I have probably changed something via menuconfig, but I still
>>>> would have thought/hoped that this sort of behaviour wouldn't happen
>>>> regardless?
>>>>
>>>> Anyone got any suggestions or hints (other than go back to school!)?
>>>
>>> Have you tried installing signal handlers for SIGQUIT and SIGINT and
>>> ensuring that the files are closed before the program is quit?
>>>
>>> Nathan
>>
>> SIGINT, SIGKILL, etc. don't do graceful shutdowns like exit() does.
>> They should behave as though _exit() were called which does an
>> immediate termination. However, _exit() is still required to close
>> all open file descriptor (Per Linux man page) and, if it does not,
>> that would be a bug.
>>
>> SIGKILL can't be caught (again per the Linux man page)
>>
>> https://man7.org/linux/man-pages/man2/exit.2.html
>> https://man7.org/linux/man-pages/man7/signal.7.html
>>
>"Closing" per se is probably not a the root of the problem when the file
>descriptors are deallocated when the task group terminates, all of the
>descriptors are freed. However, I suspect the there may be an open
>reference count in the drivers which is not decrements and whcih could
>subsequently in interfere with the correct behavior or a driver.
>
>
Aha! Yes, I added open counts just a few days ago so that is most likely it. I
understand it all a bit better now (which is why I asked) so thank you Gregory.
I will check other drivers that use open counts and see what daft thing I've
done this time <roll eyes>
