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To:     Thomas Gleixner <tglx@linutronix.de>,
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References: <20200318204302.693307984@linutronix.de>
 <20200318204408.521507446@linutronix.de>
From:   Logan Gunthorpe <logang@deltatee.com>
Message-ID: <9bb6db07-12c4-c272-3a98-baed2ac2f738@deltatee.com>
Date:   Wed, 18 Mar 2020 16:28:34 -0600
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Subject: Re: [patch V2 11/15] completion: Use simple wait queues
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On 2020-03-18 2:43 p.m., Thomas Gleixner wrote:
> There is no semantical or functional change:
> 
>   - completions use the exclusive wait mode which is what swait provides
> 
>   - complete() wakes one exclusive waiter
> 
>   - complete_all() wakes all waiters while holding the lock which protects
>     the wait queue against newly incoming waiters. The conversion to swait
>     preserves this behaviour.
> 
> complete_all() might cause unbound latencies with a large number of waiters
> being woken at once, but most complete_all() usage sites are either in
> testing or initialization code or have only a really small number of
> concurrent waiters which for now does not cause a latency problem. Keep it
> simple for now.

Seems like it would be worth adding a note for this to the
complete_all() doc string. Otherwise developers will not likely find out
about this issue and may not keep it as simple as you'd like.

Logan