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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 29 Jun 2017 13:57:41 -0700
Message-ID: <CA+55aFyCMha0Q1=wRFP-Xa93SHvr97sa1bzJDsx0m3=GyiqADw@mail.gmail.com>
Subject: Re: [PATCH 2/4] swait: add the missing killable swaits
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg KH <gregkh@linuxfoundation.org>, mfuzzey@parkeon.com,
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On Thu, Jun 29, 2017 at 12:40 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> On Thu, Jun 29, 2017 at 11:59:29AM -0700, Linus Torvalds wrote:
>> > at a time... I'm probably missing your point here.
>>
>> The *reason* they wake up only one seems to be that there really is
>> just one. It's some per-cpu idle thread for kvm, and for RCU it's the
>> RCU workqueue thread.
>>
>> So the queue literally looks suspiciously pointless.
>>
>> But I might be wrong, and there can actually be multiple entries.
>
> Since this swake_up() --> swake_up_all() reportedly *fixed* the one wake up
> issue it would seem this does queue [0].

I'm not talking about the firmware code.

That thing never had an excuse to use swait in the first place.

I'm talking about kvm and rcu, which *do* have excuses to use it, but
where I argue that swait is _still_ a questionable interface for other
reasons.

                Linus