1/*
2 * Copyright 2016 Jakub Klama <jceel@FreeBSD.org>
3 * All rights reserved
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted providing that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
16 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
18 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
22 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
23 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
24 * POSSIBILITY OF SUCH DAMAGE.
25 *
26 */
27
28#ifndef	LIB9P_THREADPOOL_H
29#define	LIB9P_THREADPOOL_H
30
31#include <stdbool.h>
32#include <pthread.h>
33#include <sys/queue.h>
34#include "lib9p.h"
35
36STAILQ_HEAD(l9p_request_queue, l9p_request);
37
38/*
39 * Most of the workers in the threadpool run requests.
40 *
41 * One distinguished worker delivers responses from the
42 * response queue.  The reason this worker exists is to
43 * guarantee response order, so that flush responses go
44 * after their flushed requests.
45 */
46struct l9p_threadpool {
47    struct l9p_connection *	ltp_conn;	/* the connection */
48    struct l9p_request_queue	ltp_workq;	/* requests awaiting a worker */
49    struct l9p_request_queue	ltp_replyq;	/* requests that are done */
50    pthread_mutex_t		ltp_mtx;	/* locks queues and cond vars */
51    pthread_cond_t		ltp_work_cv;	/* to signal regular workers */
52    pthread_cond_t		ltp_reply_cv;	/* to signal reply-worker */
53    LIST_HEAD(, l9p_worker)	ltp_workers;	/* list of all workers */
54};
55
56/*
57 * All workers, including the responder, use this as their
58 * control structure.  (The only thing that distinguishes the
59 * responder is that it runs different code and waits on the
60 * reply_cv.)
61 */
62struct l9p_worker {
63    struct l9p_threadpool *	ltw_tp;
64    pthread_t			ltw_thread;
65    bool			ltw_exiting;
66    bool			ltw_responder;
67    LIST_ENTRY(l9p_worker)	ltw_link;
68};
69
70/*
71 * Each request has a "work state" telling where the request is,
72 * in terms of workers working on it.  That is, this tells us
73 * which threadpool queue, if any, the request is in now or would
74 * go in, or what's happening with it.
75 */
76enum l9p_workstate {
77	L9P_WS_NOTSTARTED,		/* not yet started */
78	L9P_WS_IMMEDIATE,		/* Tflush being done sans worker */
79	L9P_WS_INPROGRESS,		/* worker is working on it */
80	L9P_WS_RESPQUEUED,		/* worker is done, response queued */
81	L9P_WS_REPLYING,		/* responder is in final reply path */
82};
83
84/*
85 * Each request has a "flush state", initally NONE meaning no
86 * Tflush affected the request.
87 *
88 * If a Tflush comes in before we ever assign a work thread,
89 * the flush state goes to FLUSH_REQUESTED_PRE_START.
90 *
91 * If a Tflush comes in after we assign a work thread, the
92 * flush state goes to FLUSH_REQUESTED_POST_START.  The flush
93 * request may be too late: the request might finish anyway.
94 * Or it might be soon enough to abort.  In all cases, though, the
95 * operation requesting the flush (the "flusher") must wait for
96 * the other request (the "flushee") to go through the respond
97 * path.  The respond routine gets to decide whether to send a
98 * normal response, send an error, or drop the request
99 * entirely.
100 *
101 * There's one especially annoying case: what if a Tflush comes in
102 * *while* we're sending a response?  In this case it's too late:
103 * the flush just waits for the fully-composed response.
104 */
105enum l9p_flushstate {
106	L9P_FLUSH_NONE = 0,		/* must be zero */
107	L9P_FLUSH_REQUESTED_PRE_START,	/* not even started before flush */
108	L9P_FLUSH_REQUESTED_POST_START,	/* started, then someone said flush */
109	L9P_FLUSH_TOOLATE		/* too late, already responding */
110};
111
112void	l9p_threadpool_flushee_done(struct l9p_request *);
113int	l9p_threadpool_init(struct l9p_threadpool *, int);
114void	l9p_threadpool_run(struct l9p_threadpool *, struct l9p_request *);
115int	l9p_threadpool_shutdown(struct l9p_threadpool *);
116int	l9p_threadpool_tflush(struct l9p_request *);
117
118#endif	/* LIB9P_THREADPOOL_H  */
119