linux-kernel - Re: [RFC 0/5] iwlwifi: enhance final opmode work

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Message-ID: <1488352350.2698.1.camel@sipsolutions.net>
Date:   Wed, 01 Mar 2017 08:12:30 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>, luciano.coelho@...el.com,
        emmanuel.grumbach@...el.com, tj@...nel.org, arjan@...ux.intel.com,
        ming.lei@...onical.com, zajec5@...il.com
Cc:     jeyu@...hat.com, rusty@...tcorp.com.au, pmladek@...e.com,
        gregkh@...uxfoundation.org, linuxwifi@...el.com,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/5] iwlwifi: enhance final opmode work

> One of the limitations of using async_schedule() though is we cannot
> request_module() synchronously on async calls given that the module
> initialization code will call async_synchronize_full() if the module
> being initialized happened to have used async work on its
> initialization routine, otherwise we'd deadlock.
> 
> So, I either I change back to workqueus or we live happy with either:

I really think you should avoid breaking this API and change back.
Drivers have been using it, how to avoid the use-after-free with a
completion is well known, and there's generally no issue.

Making things "easier" while requiring lots of churn everywhere isn't
always a good thing.

If you end up introducing some new API then perhaps that new API would
make sense to use async_schedule(), but I don't really see all that
much point in changing all of this now.

johannes