Received-SPF: pass (google.com: domain of linux-kernel+bounces-208808-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Mon, 10 Jun 2024 21:42:08 +0200
From: Frederic Weisbecker <frederic@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-tip-commits@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>, stable@vger.kernel.org,
	x86@kernel.org
Subject: Re: [tip: timers/urgent] tick/nohz_full: Don't abuse
 smp_call_function_single() in tick_setup_device()
Message-ID: <ZmdXEDOdM8Oe4gl_@pavilion.home>
References: <20240528122019.GA28794@redhat.com>
 <171804398181.10875.7931386382573929520.tip-bot2@tip-bot2>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <171804398181.10875.7931386382573929520.tip-bot2@tip-bot2>

Le Mon, Jun 10, 2024 at 06:26:21PM -0000, tip-bot2 for Oleg Nesterov a ?crit :
> The following commit has been merged into the timers/urgent branch of tip:
> 
> Commit-ID:     07c54cc5988f19c9642fd463c2dbdac7fc52f777
> Gitweb:        https://git.kernel.org/tip/07c54cc5988f19c9642fd463c2dbdac7fc52f777
> Author:        Oleg Nesterov <oleg@redhat.com>
> AuthorDate:    Tue, 28 May 2024 14:20:19 +02:00
> Committer:     Thomas Gleixner <tglx@linutronix.de>
> CommitterDate: Mon, 10 Jun 2024 20:18:13 +02:00
> 
> tick/nohz_full: Don't abuse smp_call_function_single() in tick_setup_device()
> 
> After the recent commit 5097cbcb38e6 ("sched/isolation: Prevent boot crash
> when the boot CPU is nohz_full") the kernel no longer crashes, but there is
> another problem.
> 
> In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
> update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
> in smp_call_function_single().
> 
> Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
> comment explains why this is safe (thanks Thomas!).
> 
> Fixes: 08ae95f4fd3b ("nohz_full: Allow the boot CPU to be nohz_full")
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
> Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com

I think we agreed on that version actually:

https://lore.kernel.org/all/20240603153557.GA8311@redhat.com/

Thanks.