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From: Valentin Schneider <valentin.schneider@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>,
	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>,
	kernel-team@android.com
Subject: Re: [PATCH v3 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity
Date: Thu, 19 Nov 2020 16:57:22 +0000	[thread overview]
Message-ID: <jhj4kllwahv.mognet@arm.com> (raw)
In-Reply-To: <20201119160944.GP3121392@hirez.programming.kicks-ass.net>


On 19/11/20 16:09, Peter Zijlstra wrote:
> On Thu, Nov 19, 2020 at 01:13:20PM +0000, Will Deacon wrote:
>
>> Sure, but I was talking about what userspace sees, and I don't think it ever
>> sees CPUs that have been hotplugged off, right? That is, sched_getaffinity()
>> masks its result with the active_mask.
>
> # for i in /sys/devices/system/cpu/cpu*/online; do echo -n $i ":"; cat $i; done
> /sys/devices/system/cpu/cpu1/online :0
> /sys/devices/system/cpu/cpu2/online :1
> /sys/devices/system/cpu/cpu3/online :1
> /sys/devices/system/cpu/cpu4/online :1
> /sys/devices/system/cpu/cpu5/online :1
> /sys/devices/system/cpu/cpu6/online :1
> /sys/devices/system/cpu/cpu7/online :1
>
> # grep Cpus_allowed /proc/self/status
> Cpus_allowed:   ff
> Cpus_allowed_list:      0-7
>
>
> :-)

Harumph, so there is that...

$ while true; do continue; done &
$ PID=$!
$ taskset -pc 0-1 $PID
  pid 849's current affinity list: 0-5
  pid 849's new affinity list: 0,1
$ echo 0 > /sys/devices/system/cpu/cpu1/online
  [12578.545726] CPU1: shutdown
  [12578.548454] psci: CPU1 killed (polled 0 ms)
$ taskset -pc $PID
  pid 849's current affinity list: 0
$ cat /proc/$PID/status | grep Cpus
  Cpus_allowed:   03
  Cpus_allowed_list:      0-1

  reply	other threads:[~2020-11-19 16:57 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-13  9:37 [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Will Deacon
2020-11-13  9:37 ` [PATCH v3 01/14] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-11-13  9:37 ` [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-11-19 11:27   ` Valentin Schneider
2020-11-19 13:12     ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-11-13  9:37 ` [PATCH v3 04/14] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-11-13  9:37 ` [PATCH v3 05/14] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-11-13  9:37 ` [PATCH v3 06/14] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2020-11-13  9:37 ` [PATCH v3 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Will Deacon
2020-11-19  9:18   ` Quentin Perret
2020-11-19 11:03     ` Quentin Perret
2020-11-19 11:05     ` Will Deacon
2020-11-19 11:27       ` Valentin Schneider
2020-11-19 13:13         ` Will Deacon
2020-11-19 14:54           ` Valentin Schneider
2020-11-19 16:41             ` Will Deacon
2020-11-19 12:47   ` Valentin Schneider
2020-11-19 13:13     ` Will Deacon
2020-11-19 14:54       ` Valentin Schneider
2020-11-19 16:09       ` Peter Zijlstra
2020-11-19 16:57         ` Valentin Schneider [this message]
2020-11-19 19:25           ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2020-11-19  9:24   ` Quentin Perret
2020-11-19 11:06     ` Will Deacon
2020-11-19 16:19       ` Peter Zijlstra
2020-11-19 16:30         ` Will Deacon
2020-11-19 16:44           ` Peter Zijlstra
2020-11-19 16:51             ` Will Deacon
2020-11-19 16:14   ` Peter Zijlstra
2020-11-19 16:28     ` Will Deacon
2020-11-19 16:42       ` Peter Zijlstra
2020-11-19 16:48         ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2020-11-19  9:29   ` Quentin Perret
2020-11-19 11:06     ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 10/14] sched: Introduce arch_cpu_allowed_mask() to limit fallback rq selection Will Deacon
2020-11-19  9:38   ` Quentin Perret
2020-11-19 11:07     ` Will Deacon
2020-11-19 20:39       ` Will Deacon
2020-11-23 14:48         ` Quentin Perret
2020-11-13  9:37 ` [PATCH v3 11/14] sched: Reject CPU affinity changes based on arch_cpu_allowed_mask() Will Deacon
2020-11-19  9:47   ` Quentin Perret
2020-11-19 11:07     ` Will Deacon
2020-11-19 14:30       ` Quentin Perret
2020-11-19 16:44         ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 12/14] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2020-11-13  9:37 ` [PATCH v3 13/14] arm64: Implement arch_cpu_allowed_mask() Will Deacon
2020-11-13  9:37 ` [PATCH v3 14/14] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2020-11-19 16:11 ` [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Peter Zijlstra
2020-11-19 16:39   ` Will Deacon

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