From: Thomas Gleixner <tglx@linutronix.de>
To: David Woodhouse <dwmw2@infradead.org>,
Usama Arif <usama.arif@bytedance.com>,
kim.phillips@amd.com, brgerst@gmail.com
Cc: piotrgorski@cachyos.org, oleksandr@natalenko.name,
arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org,
pbonzini@redhat.com, paulmck@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com,
thomas.lendacky@amd.com, seanjc@google.com,
pmenzel@molgen.mpg.de, fam.zheng@bytedance.com,
punit.agrawal@bytedance.com, simon.evans@bytedance.com,
liangma@liangbit.com, gpiccoli@igalia.com
Subject: Re: [PATCH v16 3/8] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU
Date: Fri, 24 Mar 2023 10:46:08 +0100 [thread overview]
Message-ID: <87sfdu7a8v.ffs@tglx> (raw)
In-Reply-To: <87v8ir6j96.ffs@tglx>
On Fri, Mar 24 2023 at 02:16, Thomas Gleixner wrote:
> On Thu, Mar 23 2023 at 23:12, David Woodhouse wrote:
> So surely you could claim that up to #6 (TSC sync) nothing needs to
> synchronize.
>
> But that's simply not true because topology information is implicitely
> serialized by CPU hotplug and your attempt to serialize that in patch
> 7/8 is not cutting it at all because AP #4 (STARTING) callbacks rely
> implicitely on the immutability of the topology information and so do
> some of the later (threaded) AP callbacks too.
It's even worse. Any topology relevant change _must_ be serialized by
holding cpu_hotplug_lock write locked. So this needs fundamentally more
thought than just slapping a few misnomed states into the picture and
pretending that everything else just works.
Thanks,
tglx
next prev parent reply other threads:[~2023-03-24 9:46 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 19:40 [PATCH v16 0/8] Parallel CPU bringup for x86_64 Usama Arif
2023-03-21 19:40 ` [PATCH v16 1/8] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h> Usama Arif
2023-03-21 19:40 ` [PATCH v16 2/8] cpu/hotplug: Reset task stack state in _cpu_up() Usama Arif
2023-03-22 11:06 ` Mark Rutland
2023-03-21 19:40 ` [PATCH v16 3/8] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU Usama Arif
2023-03-23 22:36 ` Thomas Gleixner
2023-03-23 22:49 ` David Woodhouse
2023-03-23 23:48 ` Thomas Gleixner
2023-03-24 0:06 ` David Woodhouse
2023-03-23 23:05 ` Thomas Gleixner
2023-03-23 23:12 ` David Woodhouse
2023-03-24 1:16 ` Thomas Gleixner
2023-03-24 9:31 ` David Woodhouse
2023-03-24 13:57 ` Thomas Gleixner
2023-03-24 15:33 ` David Woodhouse
2023-03-24 14:07 ` Thomas Gleixner
2023-03-24 9:46 ` Thomas Gleixner [this message]
2023-03-24 10:00 ` David Woodhouse
2023-03-27 18:48 ` David Woodhouse
2023-03-21 19:40 ` [PATCH v16 4/8] x86/smpboot: Split up native_cpu_up into separate phases and document them Usama Arif
2023-03-21 19:40 ` [PATCH v16 5/8] x86/smpboot: Support parallel startup of secondary CPUs Usama Arif
2023-03-21 19:40 ` [PATCH v16 6/8] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Usama Arif
2023-03-21 19:40 ` [PATCH v16 7/8] x86/smpboot: Serialize topology updates for secondary bringup Usama Arif
2023-03-21 19:40 ` [PATCH v16 8/8] x86/smpboot: Allow parallel bringup for SEV-ES Usama Arif
2023-03-22 22:47 ` Borislav Petkov
2023-03-23 8:32 ` David Woodhouse
2023-03-23 8:51 ` Borislav Petkov
2023-03-23 9:04 ` David Woodhouse
2023-03-23 14:23 ` Brian Gerst
2023-03-27 17:47 ` Borislav Petkov
2023-03-27 18:14 ` David Woodhouse
2023-03-27 19:14 ` Tom Lendacky
2023-03-27 19:32 ` Borislav Petkov
2023-03-23 13:16 ` Tom Lendacky
[not found] ` <751f572f940220775054dc09324b20b929d7d66d.camel@amazon.co.uk>
2023-03-23 18:28 ` Tom Lendacky
2023-03-23 22:13 ` Borislav Petkov
2023-03-23 22:30 ` [EXTERNAL][PATCH " David Woodhouse
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