[<prev] [next>] [day] [month] [year] [list]
Date: Wed, 7 Jul 2021 12:42:26 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Valentin Schneider <valentin.schneider@....com>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Frederic Weisbecker <frederic@...nel.org>,
Alexey Kardashevskiy <aik@...abs.ru>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] s390: preempt: Fix preempt_count initialization
On Wed, Jul 07, 2021 at 05:33:38PM +0100, Valentin Schneider wrote:
> S390's init_idle_preempt_count(p, cpu) doesn't actually let us initialize the
> preempt_count of the requested CPU's idle task: it unconditionally writes
> to the current CPU's. This clearly conflicts with idle_threads_init(),
> which intends to initialize *all* the idle tasks, including their
> preempt_count (or their CPU's, if the arch uses a per-CPU preempt_count).
>
> Unfortunately, it seems the way s390 does things doesn't let us initialize
> every possible CPU's preempt_count early on, as the pages where this
> resides are only allocated when a CPU is brought up and are freed when it
> is brought down.
>
> Let the arch-specific code set a CPU's preempt_count when its lowcore is
> allocated, and turn init_idle_preempt_count() into an empty stub.
>
> Fixes: f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled")
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Guenter
Powered by blists - more mailing lists