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From: Will Deacon <will@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Qais Yousef <qais.yousef@arm.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	kernel-team@android.com
Subject: Re: [PATCH v6 06/21] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection
Date: Mon, 24 May 2021 13:17:43 +0100	[thread overview]
Message-ID: <20210524121743.GC14913@willie-the-truck> (raw)
In-Reply-To: <20210521160344.GJ5618@worktop.programming.kicks-ass.net>

On Fri, May 21, 2021 at 06:03:44PM +0200, Peter Zijlstra wrote:
> On Tue, May 18, 2021 at 10:47:10AM +0100, Will Deacon wrote:
> > diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
> > index 03dee12d2b61..bc4ac3c525e6 100644
> > --- a/include/linux/mmu_context.h
> > +++ b/include/linux/mmu_context.h
> > @@ -14,4 +14,12 @@
> >  static inline void leave_mm(int cpu) { }
> >  #endif
> >  
> > +/*
> > + * CPUs that are capable of running task @p. By default, we assume a sane,
> > + * homogeneous system. Must contain at least one active CPU.
> > + */
> > +#ifndef task_cpu_possible_mask
> > +# define task_cpu_possible_mask(p)	cpu_possible_mask
> > +#endif
> 
> #ifndef task_cpu_possible_mask
> # define task_cpu_possible_mask(p)	cpu_possible_mask
> # define task_cpu_possible(cpu, p)	true
> #else
> # define task_cpu_possible(cpu, p)	cpumask_test_cpu((cpu), task_cpu_possible_mask(p))
> #endif
> 
> > +
> >  #endif
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 5226cc26a095..482f7fdca0e8 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -1813,8 +1813,11 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
> >  		return cpu_online(cpu);
> >  
> >  	/* Non kernel threads are not allowed during either online or offline. */
> >  	if (!(p->flags & PF_KTHREAD))
> > -		return cpu_active(cpu);
> +		return cpu_active(cpu) && task_cpu_possible(cpu, p);
> 
> >  	/* KTHREAD_IS_PER_CPU is always allowed. */
> >  	if (kthread_is_per_cpu(p))
> 
> Would something like that make sense?

I think this is probably the only place that we could use the helper, but
it's also one of the places where architectures that don't have to worry
about asymmetry end up with the check so, yes, I'll do that for v7.

Will

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  reply	other threads:[~2021-05-24 21:48 UTC|newest]

Thread overview: 83+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-18  9:47 [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-05-18  9:47 ` [PATCH v6 01/21] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2021-05-21 10:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 02/21] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2021-05-21 10:25   ` Catalin Marinas
2021-05-24 12:05     ` Will Deacon
2021-05-24 13:49       ` Catalin Marinas
2021-05-21 10:41   ` Catalin Marinas
2021-05-24 12:09     ` Will Deacon
2021-05-24 13:46       ` Catalin Marinas
2021-05-21 15:22   ` Qais Yousef
2021-05-24 20:21     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 03/21] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2021-05-21 10:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 04/21] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2021-05-21 10:55   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 05/21] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-05-21 11:00   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 06/21] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2021-05-21 16:03   ` Peter Zijlstra
2021-05-24 12:17     ` Will Deacon [this message]
2021-05-18  9:47 ` [PATCH v6 07/21] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-05-21 17:39   ` Qais Yousef
2021-05-24 20:21     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 08/21] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-05-21 16:25   ` Qais Yousef
2021-05-24 21:09     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 09/21] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-05-18  9:47 ` [PATCH v6 10/21] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-05-18  9:47 ` [PATCH v6 11/21] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-05-21 16:41   ` Qais Yousef
2021-05-24 21:16     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 12/21] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-05-21 17:11   ` Qais Yousef
2021-05-24 21:43     ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 13/21] sched: Admit forcefully-affined tasks into SCHED_DEADLINE Will Deacon
2021-05-18 10:20   ` Quentin Perret
2021-05-18 10:28     ` Will Deacon
2021-05-18 10:48       ` Quentin Perret
2021-05-18 10:59         ` Will Deacon
2021-05-18 13:19           ` Quentin Perret
2021-05-20  9:13             ` Juri Lelli
2021-05-20 10:16               ` Will Deacon
2021-05-20 10:33                 ` Quentin Perret
2021-05-20 12:38                   ` Juri Lelli
2021-05-20 12:38                   ` Daniel Bristot de Oliveira
2021-05-20 15:06                     ` Dietmar Eggemann
2021-05-20 16:00                       ` Daniel Bristot de Oliveira
2021-05-20 17:55                         ` Dietmar Eggemann
2021-05-20 18:03                           ` Will Deacon
2021-05-21 11:26                             ` Dietmar Eggemann
2021-05-20 18:01                     ` Will Deacon
2021-05-21  5:25                       ` Juri Lelli
2021-05-21  8:15                         ` Quentin Perret
2021-05-21  8:39                           ` Juri Lelli
2021-05-21 10:37                             ` Will Deacon
2021-05-21 11:23                               ` Dietmar Eggemann
2021-05-21 13:02                                 ` Quentin Perret
2021-05-21 14:04                                   ` Juri Lelli
2021-05-21 17:47                                     ` Dietmar Eggemann
2021-05-21 13:00                               ` Daniel Bristot de Oliveira
2021-05-21 13:12                                 ` Quentin Perret
2021-05-24 20:47                                 ` Will Deacon
2021-05-18  9:47 ` [PATCH v6 14/21] freezer: Add frozen_or_skipped() helper function Will Deacon
2021-05-18  9:47 ` [PATCH v6 15/21] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Will Deacon
2021-05-18  9:47 ` [PATCH v6 16/21] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-05-24 14:57   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 17/21] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-05-24 15:02   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 18/21] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-05-24 15:46   ` Catalin Marinas
2021-05-24 20:32     ` Will Deacon
2021-05-25  9:43       ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 19/21] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-05-24 15:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 20/21] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-05-24 15:47   ` Catalin Marinas
2021-05-18  9:47 ` [PATCH v6 21/21] Documentation: arm64: describe asymmetric 32-bit support Will Deacon
2021-05-21 17:37   ` Qais Yousef
2021-05-24 21:46     ` Will Deacon
2021-05-24 16:22   ` Catalin Marinas
2021-05-21 17:45 ` [PATCH v6 00/21] Add support for 32-bit tasks on asymmetric AArch32 systems Qais Yousef
2021-05-24 22:08   ` Will Deacon

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