Re: [PATCH 2/4] swait: add the missing killable swaits

Linus Torvalds
2017-06-29T20:57:41Z

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