From: John Ogness <john.ogness@linutronix.de>
To: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: pmladek@suse.com, "Paul E. McKenney" <paulmck@kernel.org>,
rcu <rcu@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
Julia.Lawall@inria.fr, paulus@samba.org, lance@osuosl.org,
ldufour@linux.ibm.com,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH linux-next] powerpc: use raw_smp_processor_id in arch_touch_nmi_watchdog
Date: Thu, 14 Jul 2022 13:52:37 +0206 [thread overview]
Message-ID: <87pmi77w82.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <CAABZP2x-OiwX7-nRvdPz0NU1D5kgUoL4MQOgTqLK1KgLcrZ5DA@mail.gmail.com>
On 2022-07-14, Zhouyi Zhou <zhouzhouyi@gmail.com> wrote:
> Thank John for correcting me ;-)
After looking more closely, I do not think disabling migration is the
correct fix either.
The per-cpu variable @wd_timer_tb is written from 2 functions:
- watchdog_timer_interrupt() <-- irq handler
- arch_touch_nmi_watchdog() <-- called from preemptible
Since watchdog_timer_interrupt() is called from irq context, I expect
that interrupts need to be disabled for the update in
arch_touch_nmi_watchdog(). Perhaps a using a per-cpu local_lock_t with
local_lock_irqsave() to protect write access to @wd_timer_tb?
John Ogness
WARNING: multiple messages have this Message-ID (diff)
From: John Ogness <john.ogness@linutronix.de>
To: Zhouyi Zhou <zhouzhouyi@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
paulus@samba.org, Nicholas Piggin <npiggin@gmail.com>,
ldufour@linux.ibm.com, pmladek@suse.com, Julia.Lawall@inria.fr,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
lance@osuosl.org, "Paul E. McKenney" <paulmck@kernel.org>,
rcu <rcu@vger.kernel.org>
Subject: Re: [PATCH linux-next] powerpc: use raw_smp_processor_id in arch_touch_nmi_watchdog
Date: Thu, 14 Jul 2022 13:52:37 +0206 [thread overview]
Message-ID: <87pmi77w82.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <CAABZP2x-OiwX7-nRvdPz0NU1D5kgUoL4MQOgTqLK1KgLcrZ5DA@mail.gmail.com>
On 2022-07-14, Zhouyi Zhou <zhouzhouyi@gmail.com> wrote:
> Thank John for correcting me ;-)
After looking more closely, I do not think disabling migration is the
correct fix either.
The per-cpu variable @wd_timer_tb is written from 2 functions:
- watchdog_timer_interrupt() <-- irq handler
- arch_touch_nmi_watchdog() <-- called from preemptible
Since watchdog_timer_interrupt() is called from irq context, I expect
that interrupts need to be disabled for the update in
arch_touch_nmi_watchdog(). Perhaps a using a per-cpu local_lock_t with
local_lock_irqsave() to protect write access to @wd_timer_tb?
John Ogness
next prev parent reply other threads:[~2022-07-14 11:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-14 1:31 [PATCH linux-next] powerpc: use raw_smp_processor_id in arch_touch_nmi_watchdog Zhouyi Zhou
2022-07-14 9:25 ` John Ogness
2022-07-14 10:01 ` Zhouyi Zhou
2022-07-14 10:01 ` Zhouyi Zhou
2022-07-14 11:46 ` John Ogness [this message]
2022-07-14 11:46 ` John Ogness
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