From: Michael Ellerman <mpe@ellerman.id.au>
To: Qais Yousef <qais.yousef@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Qais Yousef <qais.yousef@arm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Enrico Weigelt <info@metux.net>, Ram Pai <linuxram@us.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>,
Thiago Jung Bauermann <bauerman@linux.ibm.com>,
Christophe Leroy <christophe.leroy@c-s.fr>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/12] powerpc: Replace cpu_up/down with device_online/offline
Date: Tue, 19 Nov 2019 12:19:39 +1100 [thread overview]
Message-ID: <87h830d5n8.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20191030153837.18107-4-qais.yousef@arm.com>
Qais Yousef <qais.yousef@arm.com> writes:
> The core device API performs extra housekeeping bits that are missing
> from directly calling cpu_up/down.
>
> See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
> serialization during LPM") for an example description of what might go
> wrong.
>
> This also prepares to make cpu_up/down a private interface for anything
> but the cpu subsystem.
>
> Signed-off-by: Qais Yousef <qais.yousef@arm.com>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Michael Ellerman <mpe@ellerman.id.au>
> CC: Enrico Weigelt <info@metux.net>
> CC: Ram Pai <linuxram@us.ibm.com>
> CC: Nicholas Piggin <npiggin@gmail.com>
> CC: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> CC: Christophe Leroy <christophe.leroy@c-s.fr>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: linuxppc-dev@lists.ozlabs.org
> CC: linux-kernel@vger.kernel.org
> ---
> arch/powerpc/kernel/machine_kexec_64.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
My initial though is "what about kdump", but that function is not called
during kdump, so there should be no issue with the extra locking leading
to deadlocks in a crash.
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
I assume you haven't actually tested it?
cheers
> diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
> index 04a7cba58eff..ebf8cc7acc4d 100644
> --- a/arch/powerpc/kernel/machine_kexec_64.c
> +++ b/arch/powerpc/kernel/machine_kexec_64.c
> @@ -208,13 +208,15 @@ static void wake_offline_cpus(void)
> {
> int cpu = 0;
>
> + lock_device_hotplug();
> for_each_present_cpu(cpu) {
> if (!cpu_online(cpu)) {
> printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
> cpu);
> - WARN_ON(cpu_up(cpu));
> + WARN_ON(device_online(get_cpu_device(cpu)));
> }
> }
> + unlock_device_hotplug();
> }
>
> static void kexec_prepare_cpus(void)
> --
> 2.17.1
next prev parent reply other threads:[~2019-11-19 1:19 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191030153837.18107-1-qais.yousef@arm.com>
2019-10-30 15:38 ` [PATCH 01/12] arm64: hibernate.c: create a new function to handle cpu_up(sleep_cpu) Qais Yousef
2019-11-19 22:31 ` Thomas Gleixner
2019-11-19 22:51 ` Qais Yousef
2019-11-19 23:01 ` Thomas Gleixner
2019-11-19 23:21 ` Qais Yousef
2019-10-30 15:38 ` [PATCH 02/12] x86: Replace cpu_up/down with devcie_online/offline Qais Yousef
2019-10-30 15:38 ` [PATCH 03/12] powerpc: Replace cpu_up/down with device_online/offline Qais Yousef
2019-11-19 1:19 ` Michael Ellerman [this message]
2019-11-19 9:47 ` Qais Yousef
2019-10-30 15:38 ` [PATCH 04/12] ia64: Replace cpu_down with freeze_secondary_cpus Qais Yousef
2019-11-02 4:59 ` kbuild test robot
2019-11-19 22:21 ` Thomas Gleixner
2019-11-19 22:32 ` Qais Yousef
2019-11-19 22:59 ` Thomas Gleixner
2019-11-19 23:19 ` Qais Yousef
2019-11-20 8:46 ` Thomas Gleixner
2019-11-20 10:49 ` Qais Yousef
2019-10-30 15:38 ` [PATCH 05/12] sparc: Replace cpu_up/down with device_online/offline Qais Yousef
2019-10-30 19:33 ` David Miller
2019-10-30 15:38 ` [PATCH 06/12] parisc: " Qais Yousef
2019-11-20 11:09 ` Qais Yousef
2019-11-22 19:51 ` Helge Deller
2019-11-24 10:20 ` Qais Yousef
2019-10-30 15:38 ` [PATCH 07/12] driver: base: cpu: export device_online/offline Qais Yousef
2019-11-02 17:17 ` Greg Kroah-Hartman
2019-10-30 15:38 ` [PATCH 08/12] driver: xen: Replace cpu_up/down with device_online/offline Qais Yousef
2019-10-30 15:38 ` [PATCH 09/12] firmware: psci: " Qais Yousef
2019-10-30 15:38 ` [PATCH 10/12] torture: " Qais Yousef
2019-10-30 15:38 ` [PATCH 11/12] smp: Create a new function to bringup nonboot cpus online Qais Yousef
2019-11-19 22:42 ` Thomas Gleixner
2019-10-30 15:38 ` [PATCH 12/12] cpu: Hide cpu_up/down Qais Yousef
2019-11-19 22:25 ` Thomas Gleixner
2019-11-19 22:36 ` Qais Yousef
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