linux-kernel - Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit

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Message-ID: <87bmpnsm71.fsf@xmission.com>
Date:   Fri, 16 Jun 2017 15:37:54 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>, peterz@...radead.org,
        oleg@...hat.com, josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        paul.gortmaker@...driver.com, dmitry.torokhov@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit

"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> writes:

> On Fri, Jun 16, 2017 at 01:26:19AM +0200, Luis R. Rodriguez wrote:
>> On Thu, Jun 15, 2017 at 02:57:17PM -0700, Paul E. McKenney wrote:
>> > On Thu, Jun 15, 2017 at 11:48:18AM -0700, Luis R. Rodriguez wrote:
>> > > While reviewing RCU's interruptible swaits I noticed signals were actually
>> > > not expected. Paul explained that the reason signals are not expected is
>> > > we use kthreads, which don't get signals, furthermore the code avoided the
>> > > uninterruptible swaits as otherwise it would contribute to the system load
>> > > average on idle, bumping it from 0 to 2 or 3 (depending on preemption).
>> > > 
>> > > Since this can be confusing its best to be explicit about the requirements and
>> > > goals. This patch depends on the other killable swaits [0] recently proposed as
>> > > well interms of context. Thee patch can however be tested independently if
>> > > the hunk is addressed separately.
>> > > 
>> > > [0] https://lkml.kernel.org/r/20170614222017.14653-3-mcgrof@kernel.org
>> > 
>> > Tested-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>> > 
>> > Are you looking to push these or were you wanting me to?
>> 
>> I'd be happy for you to take them.
>
> OK, let's see if we can get some Acked-by's or Reviewed-by's from the
> relevant people.
>
> For but one example, Eric, does this look good to you or are adjustments
> needed?

Other than an unnecessary return code I don't see any issues.

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

In truth I am just barely ahead of you folks.  I ran into the same issue
the other day with a piece of my code and someone pointed me to TASK_IDLE.

Eric