From: Will Deacon <will@kernel.org> To: Quentin Perret <qperret@google.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>, 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 10/14] sched: Introduce arch_cpu_allowed_mask() to limit fallback rq selection Date: Thu, 19 Nov 2020 11:07:09 +0000 [thread overview] Message-ID: <20201119110709.GD3946@willie-the-truck> (raw) In-Reply-To: <20201119093850.GD2416649@google.com> On Thu, Nov 19, 2020 at 09:38:50AM +0000, Quentin Perret wrote: > On Friday 13 Nov 2020 at 09:37:15 (+0000), Will Deacon wrote: > > Asymmetric systems may not offer the same level of userspace ISA support > > across all CPUs, meaning that some applications cannot be executed by > > some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do > > not feature support for 32-bit applications on both clusters. > > > > On such a system, we must take care not to migrate a task to an > > unsupported CPU when forcefully moving tasks in select_fallback_rq() > > in response to a CPU hot-unplug operation. > > > > Introduce an arch_cpu_allowed_mask() hook which, given a task argument, > > allows an architecture to return a cpumask of CPUs that are capable of > > executing that task. The default implementation returns the > > cpu_possible_mask, since sane machines do not suffer from per-cpu ISA > > limitations that affect scheduling. The new mask is used when selecting > > the fallback runqueue as a last resort before forcing a migration to the > > first active CPU. > > > > Signed-off-by: Will Deacon <will@kernel.org> > > --- > > kernel/sched/core.c | 13 ++++++++++--- > > 1 file changed, 10 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 818c8f7bdf2a..8df38ebfe769 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -1696,6 +1696,11 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) > > > > #ifdef CONFIG_SMP > > > > +/* Must contain at least one active CPU */ > > +#ifndef arch_cpu_allowed_mask > > +#define arch_cpu_allowed_mask(p) cpu_possible_mask > > +#endif > > + > > /* > > * Per-CPU kthreads are allowed to run on !active && online CPUs, see > > * __set_cpus_allowed_ptr() and select_fallback_rq(). > > @@ -1708,7 +1713,10 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) > > if (is_per_cpu_kthread(p)) > > return cpu_online(cpu); > > > > - return cpu_active(cpu); > > + if (!cpu_active(cpu)) > > + return false; > > + > > + return cpumask_test_cpu(cpu, arch_cpu_allowed_mask(p)); > > } > > > > /* > > @@ -2361,10 +2369,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p) > > } > > fallthrough; > > case possible: > > - do_set_cpus_allowed(p, cpu_possible_mask); > > + do_set_cpus_allowed(p, arch_cpu_allowed_mask(p)); > > Nit: I'm wondering if this should be called arch_cpu_possible_mask() > instead? I'm open to renaming it, so if nobody else has any better ideas then I'll go with this. > In any case: > > Reviewed-by: Quentin Perret <qperret@google.com? Ta! Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org> To: Quentin Perret <qperret@google.com> 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 10/14] sched: Introduce arch_cpu_allowed_mask() to limit fallback rq selection Date: Thu, 19 Nov 2020 11:07:09 +0000 [thread overview] Message-ID: <20201119110709.GD3946@willie-the-truck> (raw) In-Reply-To: <20201119093850.GD2416649@google.com> On Thu, Nov 19, 2020 at 09:38:50AM +0000, Quentin Perret wrote: > On Friday 13 Nov 2020 at 09:37:15 (+0000), Will Deacon wrote: > > Asymmetric systems may not offer the same level of userspace ISA support > > across all CPUs, meaning that some applications cannot be executed by > > some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do > > not feature support for 32-bit applications on both clusters. > > > > On such a system, we must take care not to migrate a task to an > > unsupported CPU when forcefully moving tasks in select_fallback_rq() > > in response to a CPU hot-unplug operation. > > > > Introduce an arch_cpu_allowed_mask() hook which, given a task argument, > > allows an architecture to return a cpumask of CPUs that are capable of > > executing that task. The default implementation returns the > > cpu_possible_mask, since sane machines do not suffer from per-cpu ISA > > limitations that affect scheduling. The new mask is used when selecting > > the fallback runqueue as a last resort before forcing a migration to the > > first active CPU. > > > > Signed-off-by: Will Deacon <will@kernel.org> > > --- > > kernel/sched/core.c | 13 ++++++++++--- > > 1 file changed, 10 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 818c8f7bdf2a..8df38ebfe769 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -1696,6 +1696,11 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) > > > > #ifdef CONFIG_SMP > > > > +/* Must contain at least one active CPU */ > > +#ifndef arch_cpu_allowed_mask > > +#define arch_cpu_allowed_mask(p) cpu_possible_mask > > +#endif > > + > > /* > > * Per-CPU kthreads are allowed to run on !active && online CPUs, see > > * __set_cpus_allowed_ptr() and select_fallback_rq(). > > @@ -1708,7 +1713,10 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) > > if (is_per_cpu_kthread(p)) > > return cpu_online(cpu); > > > > - return cpu_active(cpu); > > + if (!cpu_active(cpu)) > > + return false; > > + > > + return cpumask_test_cpu(cpu, arch_cpu_allowed_mask(p)); > > } > > > > /* > > @@ -2361,10 +2369,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p) > > } > > fallthrough; > > case possible: > > - do_set_cpus_allowed(p, cpu_possible_mask); > > + do_set_cpus_allowed(p, arch_cpu_allowed_mask(p)); > > Nit: I'm wondering if this should be called arch_cpu_possible_mask() > instead? I'm open to renaming it, so if nobody else has any better ideas then I'll go with this. > In any case: > > Reviewed-by: Quentin Perret <qperret@google.com? Ta! Will _______________________________________________ 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 11:07 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 [this message] 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 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
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