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

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Message-Id: <20170615184820.22994-1-mcgrof@kernel.org>
Date:   Thu, 15 Jun 2017 11:48:18 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     peterz@...radead.org, paulmck@...ux.vnet.ibm.com, oleg@...hat.com,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com
Cc:     paul.gortmaker@...driver.com, ebiederm@...ssion.com,
        dmitry.torokhov@...il.com, linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [RFC v2 0/2] swait: add idle to make idle-hacks on kthreads explicit

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

Luis R. Rodriguez (2):
  swait: add idle variants which don't contribute to load average
  rcu: use idle versions of swait to make idle-hack clear

 include/linux/swait.h | 25 +++++++++++++++++++++++++
 kernel/rcu/tree.c     |  4 ++--
 2 files changed, 27 insertions(+), 2 deletions(-)

-- 
2.11.0