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
