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Message-ID: <1582558266.12738.32.camel@kernel.org>
Subject: Re: [PATCH RT 15/25] sched: migrate_enable: Use select_fallback_rq()
From:   Tom Zanussi <zanussi@kernel.org>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        linux-rt-users <linux-rt-users@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Carsten Emde <C.Emde@osadl.org>,
        John Kacur <jkacur@redhat.com>, Daniel Wagner <wagi@monom.org>
Date:   Mon, 24 Feb 2020 09:31:06 -0600
In-Reply-To: <20200224094349.5x6dca4tggtmmbnq@linutronix.de>
References: <cover.1582320278.git.zanussi@kernel.org>
         <eb183ce95bb3d92b426bdadf36f0648cda474379.1582320278.git.zanussi@kernel.org>
         <20200224094349.5x6dca4tggtmmbnq@linutronix.de>
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On Mon, 2020-02-24 at 10:43 +0100, Sebastian Andrzej Siewior wrote:
> On 2020-02-21 15:24:43 [-0600], zanussi@kernel.org wrote:
> > From: Scott Wood <swood@redhat.com>
> > 
> > v4.14.170-rt75-rc1 stable review patch.
> > If anyone has any objections, please let me know.
> 
> This creates bug which is stuffed later via
> 	sched: migrate_enable: Busy loop until the migration request is
> completed
> 
> So if apply this, please take the bug fix, too. This is Stevens queue
> for reference:
> > [PATCH RT 22/30] sched: migrate_enable: Use select_fallback_rq()
> 
> ^^ bug introduced
> 

Hmm, it seemed from the comment on the 4.19 series that it was '24/32
sched: migrate_enable: Use stop_one_cpu_nowait()' that required 'sched:
migrate_enable: Busy loop until the migration request is
completed' as a bug fix.

  https://lore.kernel.org/linux-rt-users/20200122083130.kuu3yppckhyjrr4u@linutronix.de/#t

I didn't take the stop_one_cpu_nowait() one, so didn't take the busy
loop one either.

Thanks,

Tom

> > [PATCH RT 23/30] sched: Lazy migrate_disable
> > processing                                                         
> >                      
> > [PATCH RT 24/30] sched: migrate_enable: Use stop_one_cpu_nowait()
> > [PATCH RT 25/30] Revert "ARM: Initialize split page table locks for
> > vector page"
> > [PATCH RT 26/30] locking: Make spinlock_t and rwlock_t a RCU
> > section on RT
> > [PATCH RT 27/30] sched/core: migrate_enable() must access
> > takedown_cpu_task on !HOTPLUG_CPU
> > [PATCH RT 28/30] lib/smp_processor_id: Adjust
> > check_preemption_disabled()
> > [PATCH RT 29/30] sched: migrate_enable: Busy loop until the
> > migration request is completed
> 
> ^^ bug fixed
> 
> Sebastian