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SubjectRe: [PATCH v2 00/15] Make the user mode driver code a better citizen
Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> On Mon, Jun 29, 2020 at 02:55:05PM -0500, Eric W. Biederman wrote:
>>
>> I have tested thes changes by booting with the code compiled in and
>> by killing "bpfilter_umh" and running iptables -vnL to restart
>> the userspace driver.
>>
>> I have compiled tested each change with and without CONFIG_BPFILTER
>> enabled.
>
> With
> CONFIG_BPFILTER=y
> CONFIG_BPFILTER_UMH=m
> it doesn't build:
>
> ERROR: modpost: "kill_pid_info" [net/bpfilter/bpfilter.ko] undefined!
>
> I've added:
> +EXPORT_SYMBOL(kill_pid_info);
> to continue testing...
>
> And then did:
> while true; do iptables -L;rmmod bpfilter; done
>
> Unfortunately sometimes 'rmmod bpfilter' hangs in wait_event().
>
> I suspect patch 13 is somehow responsible:
> + if (tgid) {
> + kill_pid_info(SIGKILL, SEND_SIG_PRIV, tgid);
> + wait_event(tgid->wait_pidfd, !pid_task(tgid, PIDTYPE_TGID));
> + bpfilter_umh_cleanup(info);
> + }
>
> I cannot figure out why it hangs. Some sort of race ?
> Since adding short delay between kill and wait makes it work.

Thanks. I will take a look.

Eric

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