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