From: Christoph Hellwig <hch@infradead.org>
To: Atish Patra <atish.patra@wdc.com>
Cc: "Patrick Stählin" <me@packi.ch>,
"Albert Ou" <aou@eecs.berkeley.edu>,
"Jason Cooper" <jason@lakedaemon.net>,
"Alan Kao" <alankao@andestech.com>,
"Dmitriy Cherkasov" <dmitriy@oss-tech.org>,
"Anup Patel" <anup@brainfault.org>,
"Daniel Lezcano" <daniel.lezcano@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Michael Clark" <michaeljclark@mac.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Marc Zyngier" <marc.zyngier@arm.com>,
"Palmer Dabbelt" <palmer@sifive.com>,
"Andreas Schwab" <schwab@suse.de>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Zong Li" <zongbox@gmail.com>
Subject: Re: [PATCH v2 1/8] RISC-V: Do not wait indefinitely in __cpu_up
Date: Thu, 17 Jan 2019 23:20:38 -0800 [thread overview]
Message-ID: <20190118072038.GA5171@infradead.org> (raw)
In-Reply-To: <1995e941-a8cf-c12e-71ae-7b50cf6c0ca5@wdc.com>
On Thu, Jan 17, 2019 at 06:35:39PM -0800, Atish Patra wrote:
> On 1/15/19 5:51 AM, Christoph Hellwig wrote:
> > > void *__cpu_up_stack_pointer[NR_CPUS];
> > > void *__cpu_up_task_pointer[NR_CPUS];
> > > +static DECLARE_COMPLETION(cpu_running);
> > > void __init smp_prepare_boot_cpu(void)
> > > {
> > > @@ -81,6 +82,7 @@ void __init setup_smp(void)
> > > int __cpu_up(unsigned int cpu, struct task_struct *tidle)
> > > {
> > > + int ret = 0;
> > > int hartid = cpuid_to_hartid_map(cpu);
> > > tidle->thread_info.cpu = cpu;
> > > @@ -96,10 +98,15 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
> > > task_stack_page(tidle) + THREAD_SIZE);
> > > WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
> > > - while (!cpu_online(cpu))
> > > - cpu_relax();
> > > + wait_for_completion_timeout(&cpu_running,
> > > + msecs_to_jiffies(1000));
> >
> > Having a global completion here worries me. I bet we have some higher
> > level serialization, but can we comment or even better lockdep assert on
> > that?
> >
>
> Yes. It is serialized from smp.c in smp_init(). It brings one cpu online
> at a time for preset_cpu mask.
>
> Do we still need a lockdep assert ?
I guess the real lock is through cpu_hotplug_lock. And yes, a comment
or even better lockdep assert would be good.
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next prev parent reply other threads:[~2019-01-18 7:20 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-08 9:38 [PATCH v2 0/8] Various SMP related fixes Atish Patra
2019-01-08 9:38 ` [PATCH v2 1/8] RISC-V: Do not wait indefinitely in __cpu_up Atish Patra
2019-01-15 13:51 ` Christoph Hellwig
2019-01-18 2:35 ` Atish Patra
2019-01-18 7:20 ` Christoph Hellwig [this message]
2019-01-08 9:38 ` [PATCH v2 2/8] RISC-V: Move cpuid to hartid mapping to SMP Atish Patra
2019-01-15 13:52 ` Christoph Hellwig
2019-01-18 2:08 ` Atish Patra
2019-01-08 9:38 ` [PATCH v2 3/8] RISC-V: Remove NR_CPUs check during hartid search from DT Atish Patra
2019-01-08 11:48 ` Anup Patel
2019-01-15 13:52 ` Christoph Hellwig
2019-01-08 9:38 ` [PATCH v2 4/8] RISC-V: Allow hartid-to-cpuid function to fail Atish Patra
2019-01-08 11:49 ` Anup Patel
2019-01-15 13:53 ` Christoph Hellwig
2019-01-08 9:38 ` [PATCH v2 5/8] RISC-V: Compare cpuid with NR_CPUS before mapping Atish Patra
2019-01-08 11:49 ` Anup Patel
2019-01-15 13:53 ` Christoph Hellwig
2019-01-08 9:38 ` [PATCH v2 6/8] RISC-V: Add required checks during clock source init Atish Patra
2019-01-08 11:56 ` Anup Patel
2019-01-18 2:10 ` Atish Patra
2019-01-15 13:54 ` Christoph Hellwig
2019-01-08 9:38 ` [PATCH v2 7/8] RISC-V: Check and continue in case of an invalid cpuid Atish Patra
2019-01-08 11:59 ` Anup Patel
2019-01-18 2:10 ` Atish Patra
2019-01-15 13:55 ` Christoph Hellwig
2019-01-08 9:38 ` [PATCH v2 8/8] RISC-V: Assign hwcap only according to current cpu Atish Patra
2019-01-08 10:33 ` Atish Patra
2019-01-08 12:01 ` Anup Patel
2019-01-15 13:56 ` Christoph Hellwig
2019-01-18 2:13 ` Atish Patra
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