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65 lines
1.7 KiB
65 lines
1.7 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* Copyright (c) 2021 Facebook |
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*/ |
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#ifndef __MMAP_UNLOCK_WORK_H__ |
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#define __MMAP_UNLOCK_WORK_H__ |
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#include <linux/irq_work.h> |
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/* irq_work to run mmap_read_unlock() in irq_work */ |
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struct mmap_unlock_irq_work { |
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struct irq_work irq_work; |
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struct mm_struct *mm; |
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}; |
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DECLARE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work); |
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/* |
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* We cannot do mmap_read_unlock() when the irq is disabled, because of |
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* risk to deadlock with rq_lock. To look up vma when the irqs are |
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* disabled, we need to run mmap_read_unlock() in irq_work. We use a |
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* percpu variable to do the irq_work. If the irq_work is already used |
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* by another lookup, we fall over. |
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*/ |
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static inline bool bpf_mmap_unlock_get_irq_work(struct mmap_unlock_irq_work **work_ptr) |
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{ |
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struct mmap_unlock_irq_work *work = NULL; |
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bool irq_work_busy = false; |
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if (irqs_disabled()) { |
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if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { |
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work = this_cpu_ptr(&mmap_unlock_work); |
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if (irq_work_is_busy(&work->irq_work)) { |
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/* cannot queue more up_read, fallback */ |
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irq_work_busy = true; |
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} |
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} else { |
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/* |
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* PREEMPT_RT does not allow to trylock mmap sem in |
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* interrupt disabled context. Force the fallback code. |
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*/ |
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irq_work_busy = true; |
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} |
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} |
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*work_ptr = work; |
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return irq_work_busy; |
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} |
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static inline void bpf_mmap_unlock_mm(struct mmap_unlock_irq_work *work, struct mm_struct *mm) |
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{ |
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if (!work) { |
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mmap_read_unlock(mm); |
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} else { |
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work->mm = mm; |
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/* The lock will be released once we're out of interrupt |
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* context. Tell lockdep that we've released it now so |
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* it doesn't complain that we forgot to release it. |
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*/ |
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rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_); |
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irq_work_queue(&work->irq_work); |
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} |
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} |
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#endif /* __MMAP_UNLOCK_WORK_H__ */
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