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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>,
	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>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH v11 07/16] sched: Split the guts of sched_setaffinity() into a helper function
Date: Wed, 18 Aug 2021 12:11:53 +0100	[thread overview]
Message-ID: <20210818111153.GA13999@willie-the-truck> (raw)
In-Reply-To: <YRznWDtF/doFRm0/@hirez.programming.kicks-ass.net>

On Wed, Aug 18, 2021 at 12:56:24PM +0200, Peter Zijlstra wrote:
> On Wed, Aug 18, 2021 at 11:50:30AM +0100, Will Deacon wrote:
> > On Tue, Aug 17, 2021 at 05:40:24PM +0200, Peter Zijlstra wrote:
> > > On Fri, Jul 30, 2021 at 12:24:34PM +0100, Will Deacon wrote:
> > > > In preparation for replaying user affinity requests using a saved mask,
> > > > split sched_setaffinity() up so that the initial task lookup and
> > > > security checks are only performed when the request is coming directly
> > > > from userspace.
> > > > 
> > > > Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
> > > > Signed-off-by: Will Deacon <will@kernel.org>
> > > 
> > > Should not sched_setaffinity() update user_cpus_ptr when it isn't NULL,
> > > such that the upcoming relax_compatible_cpus_allowed_ptr() preserve the
> > > full user mask?
> > 
> > The idea is that force_compatible_cpus_allowed_ptr() and
> > relax_compatible_cpus_allowed_ptr() are used as a pair, with the former
> > setting ->user_cpus_ptr and the latter restoring it. An intervening call
> > to sched_setaffinity() must _clear_ the saved mask, as we discussed
> > before at:
> > 
> > https://lore.kernel.org/r/YK53kDtczHIYumDC@hirez.programming.kicks-ass.net
> 
> Clearly that deserves a comment somewhere, because I keep trying to make
> it more consistent than it can be :/ I'll see if I can find a spot.

Agreed. The relax/force functions are already commented, so maybe alongside
SCA_USER?

Will

  reply	other threads:[~2021-08-18 11:13 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 11:24 [PATCH v11 00/16] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-07-30 11:24 ` [PATCH v11 01/16] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 02/16] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 03/16] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 04/16] cpuset: Cleanup cpuset_cpus_allowed_fallback() use in select_fallback_rq() Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 05/16] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 06/16] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 07/16] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-08-17 15:40   ` Peter Zijlstra
2021-08-18 10:50     ` Will Deacon
2021-08-18 10:56       ` Peter Zijlstra
2021-08-18 11:11         ` Will Deacon [this message]
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 08/16] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-08-17 15:10   ` Peter Zijlstra
2021-08-18 10:42     ` Will Deacon
2021-08-18 10:56       ` Peter Zijlstra
2021-08-18 11:53         ` Peter Zijlstra
2021-08-18 12:19           ` Will Deacon
2021-08-18 11:06       ` Peter Zijlstra
2021-08-17 15:41   ` Peter Zijlstra
2021-08-18 10:43     ` Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 09/16] sched: Introduce dl_task_check_affinity() to check proposed affinity Will Deacon
2021-08-23  9:26   ` [tip: sched/core] " tip-bot2 for Will Deacon
2021-07-30 11:24 ` [PATCH v11 10/16] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-07-30 11:24 ` [PATCH v11 11/16] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-07-30 11:24 ` [PATCH v11 12/16] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-07-30 11:24 ` [PATCH v11 13/16] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-07-30 11:24 ` [PATCH v11 14/16] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-07-30 11:24 ` [PATCH v11 15/16] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-07-30 11:24 ` [PATCH v11 16/16] Documentation: arm64: describe asymmetric 32-bit support Will Deacon

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