linux-kernel - Re: [PATCH] cpu/hotplug: remove unused check_for

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Message-ID: <20170608094134.axxwakfbqtq3kdeu@linutronix.de>
Date:   Thu, 8 Jun 2017 11:41:34 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpu/hotplug: remove unused check_for_tasks() function

On 2017-06-08 10:55:33 [+0200], Arnd Bergmann wrote:
> clang -Wunused-function found one remaining function that was
> apparently meant to be removed in a recent code cleanup:
> 
> kernel/cpu.c:565:20: warning: unused function 'check_for_tasks' [-Wunused-function]

Oh, so we lost the check while we were removing the DEAD notifier. The
teardown part of CPUHP_AP_SCHED_STARTING (which came before that check)
does migrate_tasks() => select_fallback_rq() for each task on the CPU
and will BUG() if it can't move a task away (except for kernel threads).
So I think it should be safe remove that function.
 
> Fixes: 530e9b76ae8f ("cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Sebastian