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From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will@kernel.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>,
	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>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	kernel-team@android.com
Subject: Re: [PATCH v7 13/22] sched: Allow task CPU affinity to be restricted on asymmetric systems
Date: Wed, 26 May 2021 18:30:08 +0200	[thread overview]
Message-ID: <YK53kDtczHIYumDC@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210525151432.16875-14-will@kernel.org>

On Tue, May 25, 2021 at 04:14:23PM +0100, Will Deacon wrote:
> @@ -2426,20 +2421,166 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
>  
>  	__do_set_cpus_allowed(p, new_mask, flags);
>  
> -	return affine_move_task(rq, p, &rf, dest_cpu, flags);
> +	if (flags & SCA_USER)
> +		release_user_cpus_ptr(p);
> +
> +	return affine_move_task(rq, p, rf, dest_cpu, flags);
>  
>  out:
> -	task_rq_unlock(rq, p, &rf);
> +	task_rq_unlock(rq, p, rf);
>  
>  	return ret;
>  }

So sys_sched_setaffinity() releases the user_cpus_ptr thingy ?! How does
that work?

I thought the intended semantics were somethings like:

	A - 0xff			B

	restrict(0xf) // user: 0xff eff: 0xf

					sched_setaffinity(A, 0x3c) // user: 0x3c eff: 0xc

	relax() // user: NULL, eff: 0x3c



WARNING: multiple messages have this Message-ID
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will@kernel.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>,
	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>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	kernel-team@android.com
Subject: Re: [PATCH v7 13/22] sched: Allow task CPU affinity to be restricted on asymmetric systems
Date: Wed, 26 May 2021 18:30:08 +0200	[thread overview]
Message-ID: <YK53kDtczHIYumDC@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210525151432.16875-14-will@kernel.org>

On Tue, May 25, 2021 at 04:14:23PM +0100, Will Deacon wrote:
> @@ -2426,20 +2421,166 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
>  
>  	__do_set_cpus_allowed(p, new_mask, flags);
>  
> -	return affine_move_task(rq, p, &rf, dest_cpu, flags);
> +	if (flags & SCA_USER)
> +		release_user_cpus_ptr(p);
> +
> +	return affine_move_task(rq, p, rf, dest_cpu, flags);
>  
>  out:
> -	task_rq_unlock(rq, p, &rf);
> +	task_rq_unlock(rq, p, rf);
>  
>  	return ret;
>  }

So sys_sched_setaffinity() releases the user_cpus_ptr thingy ?! How does
that work?

I thought the intended semantics were somethings like:

	A - 0xff			B

	restrict(0xf) // user: 0xff eff: 0xf

					sched_setaffinity(A, 0x3c) // user: 0x3c eff: 0xc

	relax() // user: NULL, eff: 0x3c



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  parent reply	other threads:[~2021-05-26 16:31 UTC|newest]

Thread overview: 114+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25 15:14 [PATCH v7 00/22] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-05-25 15:14 ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 01/22] sched: Favour predetermined active CPU as migration destination Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-26 11:14   ` Valentin Schneider
2021-05-26 11:14     ` Valentin Schneider
2021-05-26 12:32     ` Peter Zijlstra
2021-05-26 12:32       ` Peter Zijlstra
2021-05-26 12:36       ` Valentin Schneider
2021-05-26 12:36         ` Valentin Schneider
2021-05-26 16:03     ` Will Deacon
2021-05-26 16:03       ` Will Deacon
2021-05-26 17:46       ` Valentin Schneider
2021-05-26 17:46         ` Valentin Schneider
2021-05-25 15:14 ` [PATCH v7 02/22] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 03/22] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 04/22] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 05/22] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 06/22] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 07/22] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 08/22] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-26 15:02   ` Peter Zijlstra
2021-05-26 15:02     ` Peter Zijlstra
2021-05-26 16:07     ` Will Deacon
2021-05-26 16:07       ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 09/22] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 10/22] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-26 15:15   ` Peter Zijlstra
2021-05-26 15:15     ` Peter Zijlstra
2021-05-26 16:12     ` Will Deacon
2021-05-26 16:12       ` Will Deacon
2021-05-26 17:56       ` Peter Zijlstra
2021-05-26 17:56         ` Peter Zijlstra
2021-05-26 18:59         ` Will Deacon
2021-05-26 18:59           ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 11/22] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 12/22] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 13/22] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-26 16:20   ` Peter Zijlstra
2021-05-26 16:20     ` Peter Zijlstra
2021-05-26 16:35     ` Will Deacon
2021-05-26 16:35       ` Will Deacon
2021-05-26 16:30   ` Peter Zijlstra [this message]
2021-05-26 16:30     ` Peter Zijlstra
2021-05-26 17:02     ` Will Deacon
2021-05-26 17:02       ` Will Deacon
2021-05-27  7:56       ` Peter Zijlstra
2021-05-27  7:56         ` Peter Zijlstra
2021-05-25 15:14 ` [PATCH v7 14/22] sched: Introduce task_cpus_dl_admissible() to check proposed affinity Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 15/22] freezer: Add frozen_or_skipped() helper function Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 16/22] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-27 14:10   ` Peter Zijlstra
2021-05-27 14:10     ` Peter Zijlstra
2021-05-27 14:31     ` Peter Zijlstra
2021-05-27 14:31       ` Peter Zijlstra
2021-05-27 14:44       ` Will Deacon
2021-05-27 14:44         ` Will Deacon
2021-05-27 14:55         ` Peter Zijlstra
2021-05-27 14:55           ` Peter Zijlstra
2021-05-27 14:50       ` Peter Zijlstra
2021-05-27 14:50         ` Peter Zijlstra
2021-05-28 10:49       ` Peter Zijlstra
2021-05-28 10:49         ` Peter Zijlstra
2021-05-27 14:36     ` Will Deacon
2021-05-27 14:36       ` Will Deacon
2021-06-01  8:21   ` [RFC][PATCH] freezer,sched: Rewrite core freezer logic Peter Zijlstra
2021-06-01  8:21     ` Peter Zijlstra
2021-06-01 11:27     ` Peter Zijlstra
2021-06-01 11:27       ` Peter Zijlstra
2021-06-02 12:54       ` Will Deacon
2021-06-02 12:54         ` Will Deacon
2021-06-03 10:35         ` Peter Zijlstra
2021-06-03 10:35           ` Peter Zijlstra
2021-06-03 10:58           ` Will Deacon
2021-06-03 10:58             ` Will Deacon
2021-06-03 11:26             ` Peter Zijlstra
2021-06-03 11:26               ` Peter Zijlstra
2021-06-03 11:36               ` Will Deacon
2021-06-03 11:36                 ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 17/22] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 18/22] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 19/22] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 20/22] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 21/22] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 22/22] Documentation: arm64: describe asymmetric 32-bit support Will Deacon
2021-05-25 15:14   ` Will Deacon
2021-05-25 17:13   ` Marc Zyngier
2021-05-25 17:13     ` Marc Zyngier
2021-05-25 17:27     ` Will Deacon
2021-05-25 17:27       ` Will Deacon
2021-05-25 18:11       ` Marc Zyngier
2021-05-25 18:11         ` Marc Zyngier
2021-05-26 16:00         ` Will Deacon
2021-05-26 16:00           ` Will Deacon

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