1a96879cb3
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> Bug: 178507149 Link: https://lore.kernel.org/linux-arch/20201208132835.6151-7-will@kernel.org/ Signed-off-by: Will Deacon <willdeacon@google.com> Change-Id: I75985976c196cee7b84043e1a03fcc62f8b6d1c4
26 lines
608 B
C
26 lines
608 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_MMU_CONTEXT_H
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#define _LINUX_MMU_CONTEXT_H
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#include <asm/mmu_context.h>
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#include <asm/mmu.h>
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/* Architectures that care about IRQ state in switch_mm can override this. */
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#ifndef switch_mm_irqs_off
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# define switch_mm_irqs_off switch_mm
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#endif
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#ifndef leave_mm
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static inline void leave_mm(int cpu) { }
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#endif
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/*
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* CPUs that are capable of running task @p. By default, we assume a sane,
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* homogeneous system. Must contain at least one active CPU.
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*/
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#ifndef task_cpu_possible_mask
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# define task_cpu_possible_mask(p) cpu_possible_mask
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#endif
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#endif
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