linux-kernel - [PATCH v2 0/6] stop_machine: cleanups, fix, remove lglock

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Message-ID: <20150721192219.GA31150@redhat.com>
Date:	Tue, 21 Jul 2015 21:22:19 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/6] stop_machine: cleanups, fix, remove lglock

Hello,

Let me resend this. The only change in v2 is that I rediffed this
series against v4.2-rc3.

5/6 patch fixes the bug, I think. Say, stop_one_cpu(X) can race with
_cpu_down(X)->stop_machine() so that the kernel will crash if this
CPU X becomes online again. The window after cpu_stopper_thread()
returns and before smpboot_thread() calls ->park() is tiny, but still
this is possible afaics. But see the changelog in 6/6, I think we
should turn this cpu_stop_signal_done() into BUG() later.

6/6 removes lglock from kernel/stop_machine.c.

Peter, Rik, what do you think ?

Oleg.

 include/linux/lglock.h       |    5 --
 include/linux/stop_machine.h |   28 ++------
 kernel/cpu.c                 |    2 +-
 kernel/locking/lglock.c      |   22 ------
 kernel/stop_machine.c        |  162 ++++++++++++++++++++++++------------------
 5 files changed, 98 insertions(+), 121 deletions(-)

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