//
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// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This software is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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#ifndef CORE_REAP_H
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#define CORE_REAP_H
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#include "core/defs.h"
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#include "core/list.h"
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// nni_reap_node is to be inserted inline into structures
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// for subsystems that wish to support deferred reaping.
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// It should be zeroed at object initialization, but apart
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// from that it must not be touched directly except by the
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// reap subsystem.
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typedef struct nni_reap_node nni_reap_node;
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struct nni_reap_node {
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nni_reap_node *rn_next;
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};
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// nni_reap_list is for subsystems to define their own reap lists.
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// This allows for the reap linkage to be restricted to a single
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// pointer. Subsystems should initialize rl_offset and rl_func,
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// and leave the rest zeroed. The intention is that this is a global
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// static member for each subsystem.
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typedef struct nni_reap_list nni_reap_list;
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struct nni_reap_list {
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nni_reap_list *rl_next; // linkage in global reap list
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nni_reap_node *rl_nodes; // list of nodes to reap
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size_t rl_offset; // offset of reap_node within member.
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nni_cb rl_func; // function called to reap the item
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bool rl_inited; // initialized means it is linked in the list
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};
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// nni_reap performs an asynchronous reap of an item. This allows functions
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// it calls to acquire locks or resources without worrying about deadlocks
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// (such as from a completion callback.) The called function should avoid
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// blocking for too long if possible, since only one reap thread is present
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// in the system. The intended usage is for an nni_reap_node to be a member
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// of the structure to be reaped, and and then this function is called to
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// finalize it.
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//
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// Note that is is possible to re-queue an item to reap on the reap list.
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// This is useful if, for example, a reference count indicates that the item
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// is busy. These will be queued at the end of the reap list. This will
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// allow a dependency to defer reaping until its dependents have first been
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// reaped. HOWEVER, it is important that the item in question actually be
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// part of a fully reap-able graph; otherwise this can lead to an infinite
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// loop in the reap thread.
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extern void nni_reap(nni_reap_list *, void *);
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// nni_reap_drain waits for the reap queue to be drained.
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extern void nni_reap_drain(void);
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extern int nni_reap_sys_init(void);
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extern void nni_reap_sys_fini(void);
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#endif // CORE_REAP_H
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