From: Quentin Perret <qperret@google.com>
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>,
Peter Zijlstra <peterz@infradead.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Qais Yousef <qais.yousef@arm.com>,
Suren Baghdasaryan <surenb@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 11/14] sched: Reject CPU affinity changes based on arch_cpu_allowed_mask()
Date: Thu, 19 Nov 2020 14:30:12 +0000 [thread overview]
Message-ID: <20201119143012.GA2458028@google.com> (raw)
In-Reply-To: <20201119110723.GE3946@willie-the-truck>
On Thursday 19 Nov 2020 at 11:07:24 (+0000), Will Deacon wrote:
> Yeah, the cpuset code ignores the return value of set_cpus_allowed_ptr() in
> update_tasks_cpumask() so the failure won't be propagated, but then again I
> think that might be the right thing to do. Nothing prevents 32-bit and
> 64-bit tasks from co-existing in the same cpuseti afaict, so forcing the
> 64-bit tasks onto the 32-bit-capable cores feels much worse than the
> approach taken here imo.
Ack. And thinking about it more, failing the cgroup operation wouldn't
guarantee that the task's affinity and the cpuset are aligned anyway. We
could still exec into a 32 bit task from within a 64 bit-only cpuset.
> The interesting case is what happens if the cpuset for a 32-bit task is
> changed to contain only the 64-bit-only cores. I think that's a userspace
> bug
Maybe, but I think Android will do exactly that in some cases :/
> but the fallback rq selection should avert disaster.
I thought _this_ patch was 'fixing' this case by making the cpuset
operation pretty much a nop on the task affinity? The fallback rq stuff
is all about hotplug no?
Thanks,
Quentin
WARNING: multiple messages have this Message-ID (diff)
From: Quentin Perret <qperret@google.com>
To: Will Deacon <will@kernel.org>
Cc: linux-arch@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
kernel-team@android.com,
Vincent Guittot <vincent.guittot@linaro.org>,
Juri Lelli <juri.lelli@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-kernel@vger.kernel.org, Qais Yousef <qais.yousef@arm.com>,
Li Zefan <lizefan@huawei.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tejun Heo <tj@kernel.org>, Suren Baghdasaryan <surenb@google.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 11/14] sched: Reject CPU affinity changes based on arch_cpu_allowed_mask()
Date: Thu, 19 Nov 2020 14:30:12 +0000 [thread overview]
Message-ID: <20201119143012.GA2458028@google.com> (raw)
In-Reply-To: <20201119110723.GE3946@willie-the-truck>
On Thursday 19 Nov 2020 at 11:07:24 (+0000), Will Deacon wrote:
> Yeah, the cpuset code ignores the return value of set_cpus_allowed_ptr() in
> update_tasks_cpumask() so the failure won't be propagated, but then again I
> think that might be the right thing to do. Nothing prevents 32-bit and
> 64-bit tasks from co-existing in the same cpuseti afaict, so forcing the
> 64-bit tasks onto the 32-bit-capable cores feels much worse than the
> approach taken here imo.
Ack. And thinking about it more, failing the cgroup operation wouldn't
guarantee that the task's affinity and the cpuset are aligned anyway. We
could still exec into a 32 bit task from within a 64 bit-only cpuset.
> The interesting case is what happens if the cpuset for a 32-bit task is
> changed to contain only the 64-bit-only cores. I think that's a userspace
> bug
Maybe, but I think Android will do exactly that in some cases :/
> but the fallback rq selection should avert disaster.
I thought _this_ patch was 'fixing' this case by making the cpuset
operation pretty much a nop on the task affinity? The fallback rq stuff
is all about hotplug no?
Thanks,
Quentin
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-11-19 14:30 UTC|newest]
Thread overview: 104+ 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 ` 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 ` Will Deacon
2020-11-13 9:37 ` [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-11-13 9:37 ` Will Deacon
2020-11-19 11:27 ` Valentin Schneider
2020-11-19 11:27 ` Valentin Schneider
2020-11-19 13:12 ` Will Deacon
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 ` 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 ` 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 ` 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 ` Will Deacon
2020-11-13 9:37 ` [PATCH v3 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Will Deacon
2020-11-13 9:37 ` Will Deacon
2020-11-19 9:18 ` Quentin Perret
2020-11-19 9:18 ` Quentin Perret
2020-11-19 11:03 ` Quentin Perret
2020-11-19 11:03 ` Quentin Perret
2020-11-19 11:05 ` Will Deacon
2020-11-19 11:05 ` Will Deacon
2020-11-19 11:27 ` Valentin Schneider
2020-11-19 11:27 ` Valentin Schneider
2020-11-19 13:13 ` Will Deacon
2020-11-19 13:13 ` Will Deacon
2020-11-19 14:54 ` Valentin Schneider
2020-11-19 14:54 ` Valentin Schneider
2020-11-19 16:41 ` Will Deacon
2020-11-19 16:41 ` Will Deacon
2020-11-19 12:47 ` Valentin Schneider
2020-11-19 12:47 ` Valentin Schneider
2020-11-19 13:13 ` Will Deacon
2020-11-19 13:13 ` Will Deacon
2020-11-19 14:54 ` Valentin Schneider
2020-11-19 14:54 ` Valentin Schneider
2020-11-19 16:09 ` Peter Zijlstra
2020-11-19 16:09 ` Peter Zijlstra
2020-11-19 16:57 ` Valentin Schneider
2020-11-19 16:57 ` Valentin Schneider
2020-11-19 19:25 ` Will Deacon
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
2020-11-13 9:37 ` Will Deacon
2020-11-19 9:24 ` Quentin Perret
2020-11-19 9:24 ` Quentin Perret
2020-11-19 11:06 ` Will Deacon
2020-11-19 11:06 ` Will Deacon
2020-11-19 16:19 ` Peter Zijlstra
2020-11-19 16:19 ` Peter Zijlstra
2020-11-19 16:30 ` Will Deacon
2020-11-19 16:30 ` Will Deacon
2020-11-19 16:44 ` Peter Zijlstra
2020-11-19 16:44 ` Peter Zijlstra
2020-11-19 16:51 ` Will Deacon
2020-11-19 16:51 ` Will Deacon
2020-11-19 16:14 ` Peter Zijlstra
2020-11-19 16:14 ` Peter Zijlstra
2020-11-19 16:28 ` Will Deacon
2020-11-19 16:28 ` Will Deacon
2020-11-19 16:42 ` Peter Zijlstra
2020-11-19 16:42 ` Peter Zijlstra
2020-11-19 16:48 ` Will Deacon
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
2020-11-13 9:37 ` Will Deacon
2020-11-19 9:29 ` Quentin Perret
2020-11-19 9:29 ` Quentin Perret
2020-11-19 11:06 ` Will Deacon
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
2020-11-13 9:37 ` Will Deacon
2020-11-19 9:38 ` Quentin Perret
2020-11-19 9:38 ` Quentin Perret
2020-11-19 11:07 ` Will Deacon
2020-11-19 11:07 ` Will Deacon
2020-11-19 20:39 ` Will Deacon
2020-11-19 20:39 ` Will Deacon
2020-11-23 14:48 ` Quentin Perret
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
2020-11-13 9:37 ` Will Deacon
2020-11-19 9:47 ` Quentin Perret
2020-11-19 9:47 ` Quentin Perret
2020-11-19 11:07 ` Will Deacon
2020-11-19 11:07 ` Will Deacon
2020-11-19 14:30 ` Quentin Perret [this message]
2020-11-19 14:30 ` Quentin Perret
2020-11-19 16:44 ` Will Deacon
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 ` Will Deacon
2020-11-13 9:37 ` [PATCH v3 13/14] arm64: Implement arch_cpu_allowed_mask() Will Deacon
2020-11-13 9:37 ` 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
2020-11-13 9:37 ` Will Deacon
2020-11-19 16:11 ` [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Peter Zijlstra
2020-11-19 16:11 ` Peter Zijlstra
2020-11-19 16:39 ` Will Deacon
2020-11-19 16:39 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201119143012.GA2458028@google.com \
--to=qperret@google.com \
--cc=catalin.marinas@arm.com \
--cc=gregkh@linuxfoundation.org \
--cc=hannes@cmpxchg.org \
--cc=juri.lelli@redhat.com \
--cc=kernel-team@android.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizefan@huawei.com \
--cc=maz@kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=peterz@infradead.org \
--cc=qais.yousef@arm.com \
--cc=surenb@google.com \
--cc=tj@kernel.org \
--cc=vincent.guittot@linaro.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.