From: Will Deacon <will@kernel.org>
To: Qais Yousef <qais.yousef@arm.com>
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>,
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 12/21] sched: Allow task CPU affinity to be restricted on asymmetric systems
Date: Mon, 24 May 2021 22:43:49 +0100 [thread overview]
Message-ID: <20210524214348.GH15545@willie-the-truck> (raw)
In-Reply-To: <20210521171132.ev56j4isuxtf2zqa@e107158-lin.cambridge.arm.com>
On Fri, May 21, 2021 at 06:11:32PM +0100, Qais Yousef wrote:
> On 05/18/21 10:47, Will Deacon wrote:
> > +static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
> > + const struct cpumask *new_mask,
> > + u32 flags,
> > + struct rq *rq,
> > + struct rq_flags *rf)
> > + __releases(rq->lock)
> > + __releases(p->pi_lock)
> > {
> > const struct cpumask *cpu_valid_mask = cpu_active_mask;
> > const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
> > unsigned int dest_cpu;
> > - struct rq_flags rf;
> > - struct rq *rq;
> > int ret = 0;
> >
> > - rq = task_rq_lock(p, &rf);
> > update_rq_clock(rq);
> >
> > if (p->flags & PF_KTHREAD || is_migration_disabled(p)) {
> > @@ -2430,20 +2425,158 @@ 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);
>
> Why do we need to release the pointer here?
>
> Doesn't this mean if a 32bit task requests to change its affinity, then we'll
> lose this info and a subsequent execve() to a 64bit application means we won't
> be able to restore the original mask?
>
> ie:
>
> p0-64bit
> execve(32bit_app)
> // p1-32bit created
> p1-32bit.change_affinity()
> relase_user_cpus_ptr()
> execve(64bit_app) // lost info about p0 affinity?
>
> Hmm I think this helped me to get the answer. p1 changed its affinity, then
> there's nothing to be inherited by a new execve(), so yes we no longer need
> this info.
Yup, you got it.
> > +static int restrict_cpus_allowed_ptr(struct task_struct *p,
> > + struct cpumask *new_mask,
> > + const struct cpumask *subset_mask)
> > +{
> > + struct rq_flags rf;
> > + struct rq *rq;
> > + int err;
> > + struct cpumask *user_mask = NULL;
> > +
> > + if (!p->user_cpus_ptr)
> > + user_mask = kmalloc(cpumask_size(), GFP_KERNEL);
> > +
> > + rq = task_rq_lock(p, &rf);
> > +
> > + /*
> > + * We're about to butcher the task affinity, so keep track of what
> > + * the user asked for in case we're able to restore it later on.
> > + */
> > + if (user_mask) {
> > + cpumask_copy(user_mask, p->cpus_ptr);
> > + p->user_cpus_ptr = user_mask;
> > + }
> > +
> > + /*
> > + * Forcefully restricting the affinity of a deadline task is
> > + * likely to cause problems, so fail and noisily override the
> > + * mask entirely.
> > + */
> > + if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
> > + err = -EPERM;
> > + goto err_unlock;
>
> free(user_mark) first?
>
> > + }
> > +
> > + if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) {
> > + err = -EINVAL;
> > + goto err_unlock;
>
> ditto
We free the mask when the task exits so we don't actually need to clean up
here. I left it like this on the assumption that failing here means that
it's very likely that either the task will exit or retry very soon.
However I agree that it would be clearer to free the thing anyway, so I'll
rejig the code to do that.
Will
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next prev parent reply other threads:[~2021-05-25 2:19 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
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 [this message]
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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