On Fri, Oct 15, 2021 at 01:02:38PM +0200, Fabio M. De Francesco wrote:
> rtw_cmd_thread() "up(s)" a semaphore twice, first to notify callers when
> its execution is started and then to notify when it is about to end.
>
> It makes the same semaphore go "up" twice in the same thread. This
> construct makes Smatch to warn of duplicate "up(s)".
>
> This thread uses interruptible semaphores where instead completions are
> more suitable. For this purpose it calls an helper (_rtw_down_sema())
> that returns values that are never checked. It may lead to bugs.
>
> To address the above-mentioned issues, use two completions variables
> instead of semaphores. Use the uninterruptible versions of
> wake_for_completion*() because the interruptible / killable versions are
> not necessary.
>
> Tested with "ASUSTek Computer, Inc. Realtek 8188EUS [USB-N10 Nano]".
>
> This is an RFC patch because I'm not sure that changing this code
> from using semaphores to using completions variables is actually required.
> After all, the code was working properly with semaphores and, at the same
> time, I'm not sure if the Smatch warning about duplicate "up(s)" should
> actually be addressed.
>
> I'm waiting for Maintainers and other Reviewers to say if this patch is
> actually needed and, if so, also for suggestions about how to improve
> it. In particular I'm interested to know what they think of using the
> uninterruptible version of wait_for_completion*().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
This is basically what Arnd did to rtl8723bs in commit:
commit 09a8ea34cf431bfb77159197e46753d101c528c5
Author: Arnd Bergmann <arnd@xxxxxxxx>
Date: Mon Dec 10 22:40:30 2018 +0100
staging: rtl8723bs: change semaphores to completions
But there are some differences. His patch is a little bit cleaner
because it gets rid of "pcmdpriv->cmd_queue_sema". Could you basically
just ports Arnd's patch for this driver?
His patch goes quite a bit further as well, and change some other
semaphors but we could do it piece meal and just change the
rtw_cmd_thread() related ones.
regards,
dan carpenter
