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Groups > linux.kernel > #1349194
| From | "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [tip:smp/hotplug] cpu/hotplug: Plug death reporting race |
| Date | 2016-03-03 15:20 +0100 |
| Message-ID | <r8CgG-8cy-5@gated-at.bofh.it> (permalink) |
| References | <r8lpx-4I9-15@gated-at.bofh.it> <r8ymJ-5pr-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Mar 03, 2016 at 02:03:35AM -0800, tip-bot for Thomas Gleixner wrote:
> Commit-ID: 71f87b2fc64c2e9b6d53cb817f28711b959d3dfe
> Gitweb: http://git.kernel.org/tip/71f87b2fc64c2e9b6d53cb817f28711b959d3dfe
> Author: Thomas Gleixner <tglx@linutronix.de>
> AuthorDate: Thu, 3 Mar 2016 10:52:10 +0100
> Committer: Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Thu, 3 Mar 2016 10:52:10 +0100
>
> cpu/hotplug: Plug death reporting race
>
> Paul noticed that the conversion of the death reporting introduced a race
> where the outgoing cpu might be delayed after waking the controll processor,
> so it might not be able to call rcu_report_dead() before being physically
> removed, leading to RCU stalls.
>
> We cant call complete after rcu_report_dead(), so instead of going back to
> busy polling, simply issue a function call to do the completion.
>
> Fixes: 27d50c7eeb0f "rcu: Make CPU_DYING_IDLE an explicit call"
> Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Link: http://lkml.kernel.org/r/20160302201127.GA23440@linux.vnet.ibm.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Acked-by: Peter Zijlstra <peterz@infradead.org>
There are some possible issues with printk()s from WARN_ON() calls
using RCU from within smp_call_function_single(), but in normal
execution this should be OK. Besides, the WARN_ON() contains a
cpu_online(this_cpu), so it simply won't fire in this case.
So nice fix!!!
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/cpu.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index ff8059b..93e9d89 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -755,14 +755,26 @@ static int notify_dead(unsigned int cpu)
> return 0;
> }
>
> +static void cpuhp_complete_idle_dead(void *arg)
> +{
> + struct cpuhp_cpu_state *st = arg;
> +
> + complete(&st->done);
> +}
> +
> void cpuhp_report_idle_dead(void)
> {
> struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
>
> BUG_ON(st->state != CPUHP_AP_OFFLINE);
> - st->state = CPUHP_AP_IDLE_DEAD;
> - complete(&st->done);
> rcu_report_dead(smp_processor_id());
> + st->state = CPUHP_AP_IDLE_DEAD;
> + /*
> + * We cannot call complete after rcu_report_dead() so we delegate it
> + * to an online cpu.
> + */
> + smp_call_function_single(cpumask_first(cpu_online_mask),
> + cpuhp_complete_idle_dead, st, 0);
> }
>
> #else
>
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[patch 00/20] cpu/hotplug: Core infrastructure for cpu hotplug rework Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[patch 14/20] cpu/hotplug: Split out the state walk into functions Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Split out the state walk into functions tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 17/20] arch/hotplug: Call into idle with a proper state Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] arch/hotplug: Call into idle with a proper state tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 04/20] cpu/hotplug: Split out cpu down functions Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Split out cpu down functions tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Split out cpu down functions "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:10 +0100
[patch 03/20] cpu/hotplug: Restructure cpu_up code Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Restructure cpu_up code tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Restructure cpu_up code "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:00 +0100
[patch 16/20] cpu/hotplug: Move online calls to hotplugged cpu Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Move online calls to hotplugged cpu tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 02/20] cpu/hotplug: Restructure FROZEN state handling Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:10 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Restructure FROZEN state handling "Srivatsa S. Bhat" <srivatsa@csail.mit.edu> - 2016-03-03 00:50 +0100
[patch 11/20] cpu/hotplug: Implement setup/removal interface Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Implement setup/removal interface tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 12/20] cpu/hotplug: Move scheduler cpu_online notifier to hotplug core Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Move scheduler cpu_online notifier to hotplug core tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Let upcoming cpu bring itself fully up tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [patch 18/20] cpu/hotplug: Let upcoming cpu bring itself fully up Richard Cochran <richardcochran@gmail.com> - 2016-03-02 18:30 +0100
[patch 15/20] cpu/hotplug: Create hotplug threads Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Create hotplug threads tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 09/20] cpu/hotplug: Add sysfs state interface Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Add sysfs state interface tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Add sysfs state interface Peter Zijlstra <peterz@infradead.org> - 2016-03-02 13:50 +0100
[patch 06/20] cpu/hotplug: Convert to a state machine for the control processor Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Convert to a state machine for the control processor tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Convert to a state machine for the control processor Peter Zijlstra <peterz@infradead.org> - 2016-03-02 12:30 +0100
[patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 03:20 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 03:30 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-27 08:50 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 12:10 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-02-27 12:40 +0100
Re: [patch 20/20] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-27 17:40 +0100
[tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-03-02 21:20 +0100
Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-03-03 08:40 +0100
[tip:smp/hotplug] cpu/hotplug: Plug death reporting race tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-03 11:10 +0100
Re: [tip:smp/hotplug] cpu/hotplug: Plug death reporting race "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-03-03 15:20 +0100
[patch 08/20] cpu/hotplug: Hand in target state to _cpu_up/down Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Hand in target state to _cpu_up/down tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 19/20] cpu/hotplug: Make wait for dead cpu completion based Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 19:50 +0100
[tip:smp/hotplug] cpu/hotplug: Make wait for dead cpu completion based tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 07/20] cpu/hotplug: Convert the hotplugged cpu work to a state machine Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 20:00 +0100
[tip:smp/hotplug] cpu/hotplug: Convert the hotplugged cpu work to a state machine tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-03-01 21:00 +0100
[patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-26 20:00 +0100
Re: [patch 01/20] idle: Move x86ism out of generic code Brian Gerst <brgerst@gmail.com> - 2016-02-27 21:30 +0100
Re: [patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-29 20:40 +0100
Re: [patch 01/20] idle: Move x86ism out of generic code Will Deacon <will.deacon@arm.com> - 2016-02-29 20:50 +0100
Re: [patch 01/20] idle: Move x86ism out of generic code Thomas Gleixner <tglx@linutronix.de> - 2016-02-29 21:10 +0100
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