From: Will Deacon <will@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Will Deacon <will@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>,
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: [PATCH v6 06/21] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection
Date: Tue, 18 May 2021 10:47:10 +0100 [thread overview]
Message-ID: <20210518094725.7701-7-will@kernel.org> (raw)
In-Reply-To: <20210518094725.7701-1-will@kernel.org>
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 a task_cpu_possible_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.
Reviewed-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
include/linux/mmu_context.h | 8 ++++++++
kernel/sched/core.c | 10 ++++++----
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
index 03dee12d2b61..bc4ac3c525e6 100644
--- a/include/linux/mmu_context.h
+++ b/include/linux/mmu_context.h
@@ -14,4 +14,12 @@
static inline void leave_mm(int cpu) { }
#endif
+/*
+ * CPUs that are capable of running task @p. By default, we assume a sane,
+ * homogeneous system. Must contain at least one active CPU.
+ */
+#ifndef task_cpu_possible_mask
+# define task_cpu_possible_mask(p) cpu_possible_mask
+#endif
+
#endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5226cc26a095..482f7fdca0e8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1813,8 +1813,11 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
return cpu_online(cpu);
/* Non kernel threads are not allowed during either online or offline. */
- if (!(p->flags & PF_KTHREAD))
- return cpu_active(cpu);
+ if (!(p->flags & PF_KTHREAD)) {
+ if (cpu_active(cpu))
+ return cpumask_test_cpu(cpu, task_cpu_possible_mask(p));
+ return false;
+ }
/* KTHREAD_IS_PER_CPU is always allowed. */
if (kthread_is_per_cpu(p))
@@ -2792,10 +2795,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
*
* More yuck to audit.
*/
- do_set_cpus_allowed(p, cpu_possible_mask);
+ do_set_cpus_allowed(p, task_cpu_possible_mask(p));
state = fail;
break;
-
case fail:
BUG();
break;
--
2.31.1.751.gd2f1c929bd-goog
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next prev parent reply other threads:[~2021-05-18 9:56 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 ` Will Deacon [this message]
2021-05-21 16:03 ` [PATCH v6 06/21] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection 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
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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