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>, kernel-team@android.com Subject: [PATCH v5 06/15] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Date: Tue, 8 Dec 2020 13:28:26 +0000 [thread overview] Message-ID: <20201208132835.6151-7-will@kernel.org> (raw) In-Reply-To: <20201208132835.6151-1-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 | 8 +++++--- 2 files changed, 13 insertions(+), 3 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 e7e453492cff..58474569a2ea 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1708,7 +1708,10 @@ 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, task_cpu_possible_mask(p)); } /* @@ -2318,10 +2321,9 @@ 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, task_cpu_possible_mask(p)); state = fail; break; - case fail: BUG(); break; -- 2.29.2.576.ga3fc446d84-goog
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org> To: linux-arm-kernel@lists.infradead.org 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>, Quentin Perret <qperret@google.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>, Suren Baghdasaryan <surenb@google.com>, Ingo Molnar <mingo@redhat.com>, Li Zefan <lizefan@huawei.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Tejun Heo <tj@kernel.org>, Will Deacon <will@kernel.org>, Morten Rasmussen <morten.rasmussen@arm.com> Subject: [PATCH v5 06/15] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Date: Tue, 8 Dec 2020 13:28:26 +0000 [thread overview] Message-ID: <20201208132835.6151-7-will@kernel.org> (raw) In-Reply-To: <20201208132835.6151-1-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 | 8 +++++--- 2 files changed, 13 insertions(+), 3 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 e7e453492cff..58474569a2ea 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1708,7 +1708,10 @@ 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, task_cpu_possible_mask(p)); } /* @@ -2318,10 +2321,9 @@ 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, task_cpu_possible_mask(p)); state = fail; break; - case fail: BUG(); break; -- 2.29.2.576.ga3fc446d84-goog _______________________________________________ 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:[~2020-12-08 13:30 UTC|newest] Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-08 13:28 [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 01/15] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 02/15] arm64: Allow mismatched 32-bit EL0 support Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 03/15] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 04/15] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 05/15] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` Will Deacon [this message] 2020-12-08 13:28 ` [PATCH v5 06/15] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon 2020-12-08 13:28 ` [PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-17 12:15 ` Qais Yousef 2020-12-17 12:15 ` Qais Yousef 2020-12-17 13:44 ` Peter Zijlstra 2020-12-17 13:44 ` Peter Zijlstra 2020-12-17 14:59 ` Will Deacon 2020-12-17 14:59 ` Will Deacon 2020-12-17 15:00 ` Qais Yousef 2020-12-17 15:00 ` Qais Yousef 2020-12-08 13:28 ` [PATCH v5 08/15] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-28 3:54 ` Suren Baghdasaryan 2020-12-28 3:54 ` Suren Baghdasaryan 2020-12-08 13:28 ` [PATCH v5 09/15] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 10/15] sched: Introduce force_compatible_cpus_allowed_ptr() to limit CPU affinity Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-28 4:29 ` Suren Baghdasaryan 2020-12-28 4:29 ` Suren Baghdasaryan 2020-12-08 13:28 ` [PATCH v5 11/15] arm64: Implement task_cpu_possible_mask() Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 12/15] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 13/15] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 14/15] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-08 13:28 ` [PATCH v5 15/15] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon 2020-12-08 13:28 ` Will Deacon 2020-12-15 17:36 ` [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Peter Zijlstra 2020-12-15 17:36 ` Peter Zijlstra 2020-12-15 18:50 ` Will Deacon 2020-12-15 18:50 ` Will Deacon 2020-12-17 10:55 ` Peter Zijlstra 2020-12-17 10:55 ` Peter Zijlstra 2020-12-16 11:16 ` Qais Yousef 2020-12-16 11:16 ` Qais Yousef 2020-12-16 14:14 ` Will Deacon 2020-12-16 14:14 ` Will Deacon 2020-12-16 16:48 ` Qais Yousef 2020-12-16 16:48 ` Qais Yousef 2020-12-16 18:21 ` Suren Baghdasaryan 2020-12-16 18:21 ` Suren Baghdasaryan
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