linux-kernel - [RFC v2 0/5] rcu: Introduce for_each_leaf_node

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Date:   Thu, 15 Dec 2016 10:41:59 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Paul E . McKenney " <paulmck@...ux.vnet.ibm.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Colin King <colin.king@...onical.com>,
        Mark Rutland <mark.rutland@....com>
Subject: [RFC v2 0/5] rcu: Introduce for_each_leaf_node_cpu()

v1:

https://marc.info/?l=linux-kernel&m=148127336205765

Changes since v1:

*	Rename the primitive to for_each_leaf_node_cpu() for a shorter and
	hopefully better name

*	Fix a bug report by Colin King about bit shifting

*	Drop iterator @bit based on suggestions from Mark Rutland

*	Add a WARN_ON_ONCE() for !cpu_possible(cpu).

Based on -rcu's rcu/dev branch, commit 278c19fe5bc7 "rcu: Adjust FQS offline
checks for exact online-CPU detection". Tested by 0day and rcutorture on a
12-cpu host, the results of rcutorture are all fine except:

TREE07 ------- 7655 grace periods (4.25278 per second)
WARNING: BAD SEQ 3901:3901 last:7652 version 61
    /home/boqun/linux/tools/testing/selftests/rcutorture/res/2016.12.14-13:17:10/TREE07/console.log
WARNING: Assertion failure in /home/boqun/linux/tools/testing/selftests/rcutorture/res/2016.12.14-13:17:10/TREE07/console.log
WARNING: Summary: Stalls: 4
CPU count limited from 16 to 12

The same WARNING could be reproduced without this patchset. Paul, given the
sentence "CPU count limited from 16 to 12", is this just a problem for my
setup? Maybe I should descrease the SMP numbers or increase
rcutorture.stat_interval?

Regards,
Boqun