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>,
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>,
kernel-team@android.com
Subject: [PATCH v7 07/22] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection
Date: Tue, 25 May 2021 16:14:17 +0100 [thread overview]
Message-ID: <20210525151432.16875-8-will@kernel.org> (raw)
In-Reply-To: <20210525151432.16875-1-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 | 11 +++++++++++
kernel/sched/core.c | 5 ++---
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/include/linux/mmu_context.h b/include/linux/mmu_context.h
index 03dee12d2b61..1a599ba3524f 100644
--- a/include/linux/mmu_context.h
+++ b/include/linux/mmu_context.h
@@ -14,4 +14,15 @@
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
+# define task_cpu_possible(cpu, p) true
+#else
+# define task_cpu_possible(cpu, p) cpumask_test_cpu((cpu), task_cpu_possible_mask(p))
+#endif
+
#endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1702a60d178d..00ed51528c70 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1814,7 +1814,7 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
/* Non kernel threads are not allowed during either online or offline. */
if (!(p->flags & PF_KTHREAD))
- return cpu_active(cpu);
+ return cpu_active(cpu) && task_cpu_possible(cpu, p);
/* KTHREAD_IS_PER_CPU is always allowed. */
if (kthread_is_per_cpu(p))
@@ -2791,10 +2791,9 @@ 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;
--
2.31.1.818.g46aad6cb9e-goog
next prev parent reply other threads:[~2021-05-25 15:15 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 15:14 [PATCH v7 00/22] Add support for 32-bit tasks on asymmetric AArch32 systems Will Deacon
2021-05-25 15:14 ` [PATCH v7 01/22] sched: Favour predetermined active CPU as migration destination Will Deacon
2021-05-26 11:14 ` Valentin Schneider
2021-05-26 12:32 ` Peter Zijlstra
2021-05-26 12:36 ` Valentin Schneider
2021-05-26 16:03 ` Will Deacon
2021-05-26 17:46 ` Valentin Schneider
2021-05-25 15:14 ` [PATCH v7 02/22] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2021-05-25 15:14 ` [PATCH v7 03/22] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2021-05-25 15:14 ` [PATCH v7 04/22] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2021-05-25 15:14 ` [PATCH v7 05/22] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2021-05-25 15:14 ` [PATCH v7 06/22] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2021-05-25 15:14 ` Will Deacon [this message]
2021-05-25 15:14 ` [PATCH v7 08/22] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2021-05-26 15:02 ` Peter Zijlstra
2021-05-26 16:07 ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 09/22] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2021-05-25 15:14 ` [PATCH v7 10/22] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2021-05-26 15:15 ` Peter Zijlstra
2021-05-26 16:12 ` Will Deacon
2021-05-26 17:56 ` Peter Zijlstra
2021-05-26 18:59 ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 11/22] sched: Introduce task_struct::user_cpus_ptr to track requested affinity Will Deacon
2021-05-25 15:14 ` [PATCH v7 12/22] sched: Split the guts of sched_setaffinity() into a helper function Will Deacon
2021-05-25 15:14 ` [PATCH v7 13/22] sched: Allow task CPU affinity to be restricted on asymmetric systems Will Deacon
2021-05-26 16:20 ` Peter Zijlstra
2021-05-26 16:35 ` Will Deacon
2021-05-26 16:30 ` Peter Zijlstra
2021-05-26 17:02 ` Will Deacon
2021-05-27 7:56 ` Peter Zijlstra
2021-05-25 15:14 ` [PATCH v7 14/22] sched: Introduce task_cpus_dl_admissible() to check proposed affinity Will Deacon
2021-05-25 15:14 ` [PATCH v7 15/22] freezer: Add frozen_or_skipped() helper function Will Deacon
2021-05-25 15:14 ` [PATCH v7 16/22] sched: Defer wakeup in ttwu() for unschedulable frozen tasks Will Deacon
2021-05-27 14:10 ` Peter Zijlstra
2021-05-27 14:31 ` Peter Zijlstra
2021-05-27 14:44 ` Will Deacon
2021-05-27 14:55 ` Peter Zijlstra
2021-05-27 14:50 ` Peter Zijlstra
2021-05-28 10:49 ` Peter Zijlstra
2021-05-27 14:36 ` Will Deacon
2021-06-01 8:21 ` [RFC][PATCH] freezer,sched: Rewrite core freezer logic Peter Zijlstra
2021-06-01 11:27 ` Peter Zijlstra
2021-06-02 12:54 ` Will Deacon
2021-06-03 10:35 ` Peter Zijlstra
2021-06-03 10:58 ` Will Deacon
2021-06-03 11:26 ` Peter Zijlstra
2021-06-03 11:36 ` Will Deacon
2021-05-25 15:14 ` [PATCH v7 17/22] arm64: Implement task_cpu_possible_mask() Will Deacon
2021-05-25 15:14 ` [PATCH v7 18/22] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2021-05-25 15:14 ` [PATCH v7 19/22] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2021-05-25 15:14 ` [PATCH v7 20/22] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2021-05-25 15:14 ` [PATCH v7 21/22] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2021-05-25 15:14 ` [PATCH v7 22/22] Documentation: arm64: describe asymmetric 32-bit support Will Deacon
2021-05-25 17:13 ` Marc Zyngier
2021-05-25 17:27 ` Will Deacon
2021-05-25 18:11 ` Marc Zyngier
2021-05-26 16:00 ` Will Deacon
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