1 d3df3087 2003-12-06 devnull /* Copyright (C) 2003 Russ Cox, Massachusetts Institute of Technology */
  2 d3df3087 2003-12-06 devnull /* See COPYRIGHT */
  3 d3df3087 2003-12-06 devnull 
  4 d3df3087 2003-12-06 devnull /*
  5 d3df3087 2003-12-06 devnull  * Generic RPC packet multiplexor.  Inspired by but not derived from
  6 d3df3087 2003-12-06 devnull  * Plan 9 kernel.  Originally developed as part of Tra, later used in
  7 d3df3087 2003-12-06 devnull  * libnventi, and then finally split out into a generic library.
  8 d3df3087 2003-12-06 devnull  */
  9 d3df3087 2003-12-06 devnull 
 10 d3df3087 2003-12-06 devnull #include <u.h>
 11 d3df3087 2003-12-06 devnull #include <libc.h>
 12 d3df3087 2003-12-06 devnull #include <mux.h>
 13 d3df3087 2003-12-06 devnull 
 14 d3df3087 2003-12-06 devnull static int gettag(Mux*, Muxrpc*);
 15 d3df3087 2003-12-06 devnull static void puttag(Mux*, Muxrpc*);
 16 d3df3087 2003-12-06 devnull static void enqueue(Mux*, Muxrpc*);
 17 d3df3087 2003-12-06 devnull static void dequeue(Mux*, Muxrpc*);
 18 d3df3087 2003-12-06 devnull 
 19 d3df3087 2003-12-06 devnull void
 20 d3df3087 2003-12-06 devnull muxinit(Mux *mux)
 21 d3df3087 2003-12-06 devnull {
 22 b214663d 2004-01-09 devnull 	memset(&mux->lk, 0, sizeof(Mux)-offsetof(Mux, lk));
 23 d3df3087 2003-12-06 devnull 	mux->tagrend.l = &mux->lk;
 24 b214663d 2004-01-09 devnull 	mux->rpcfork.l = &mux->lk;
 25 d3df3087 2003-12-06 devnull 	mux->sleep.next = &mux->sleep;
 26 d3df3087 2003-12-06 devnull 	mux->sleep.prev = &mux->sleep;
 27 d3df3087 2003-12-06 devnull }
 28 d3df3087 2003-12-06 devnull 
 29 d3df3087 2003-12-06 devnull void*
 30 d3df3087 2003-12-06 devnull muxrpc(Mux *mux, void *tx)
 31 d3df3087 2003-12-06 devnull {
 32 ceb04770 2003-12-09 devnull 	int tag;
 33 d3df3087 2003-12-06 devnull 	Muxrpc *r, *r2;
 34 d3df3087 2003-12-06 devnull 	void *p;
 35 d3df3087 2003-12-06 devnull 
 36 d3df3087 2003-12-06 devnull 	/* must malloc because stack could be private */
 37 d3df3087 2003-12-06 devnull 	r = mallocz(sizeof(Muxrpc), 1);
 38 a28c0548 2005-07-13 devnull 	if(r == nil){
 39 a28c0548 2005-07-13 devnull 		werrstr("mallocz: %r");
 40 d3df3087 2003-12-06 devnull 		return nil;
 41 a28c0548 2005-07-13 devnull 	}
 42 d3df3087 2003-12-06 devnull 	r->r.l = &mux->lk;
 43 d3df3087 2003-12-06 devnull 
 44 43db87f1 2004-12-27 devnull 	/* assign the tag, add selves to response queue */
 45 ceb04770 2003-12-09 devnull 	qlock(&mux->lk);
 46 d3df3087 2003-12-06 devnull 	tag = gettag(mux, r);
 47 43db87f1 2004-12-27 devnull //print("gettag %p %d\n", r, tag);
 48 43db87f1 2004-12-27 devnull 	enqueue(mux, r);
 49 ceb04770 2003-12-09 devnull 	qunlock(&mux->lk);
 50 43db87f1 2004-12-27 devnull 
 51 43db87f1 2004-12-27 devnull 	/* actually send the packet */
 52 ceb04770 2003-12-09 devnull 	if(tag < 0 || mux->settag(mux, tx, tag) < 0 || _muxsend(mux, tx) < 0){
 53 a28c0548 2005-07-13 devnull 		werrstr("settag/send tag %d: %r", tag);
 54 a28c0548 2005-07-13 devnull 		fprint(2, "%r\n");
 55 ceb04770 2003-12-09 devnull 		qlock(&mux->lk);
 56 d165fa68 2005-01-04 devnull 		dequeue(mux, r);
 57 d3df3087 2003-12-06 devnull 		puttag(mux, r);
 58 ceb04770 2003-12-09 devnull 		qunlock(&mux->lk);
 59 d3df3087 2003-12-06 devnull 		return nil;
 60 d3df3087 2003-12-06 devnull 	}
 61 d3df3087 2003-12-06 devnull 
 62 d3df3087 2003-12-06 devnull 	qlock(&mux->lk);
 63 d3df3087 2003-12-06 devnull 	/* wait for our packet */
 64 c6687d45 2004-09-21 devnull 	while(mux->muxer && !r->p){
 65 d3df3087 2003-12-06 devnull 		rsleep(&r->r);
 66 c6687d45 2004-09-21 devnull 	}
 67 d3df3087 2003-12-06 devnull 
 68 d3df3087 2003-12-06 devnull 	/* if not done, there's no muxer: start muxing */
 69 d3df3087 2003-12-06 devnull 	if(!r->p){
 70 d3df3087 2003-12-06 devnull 		if(mux->muxer)
 71 d3df3087 2003-12-06 devnull 			abort();
 72 d3df3087 2003-12-06 devnull 		mux->muxer = 1;
 73 d3df3087 2003-12-06 devnull 		while(!r->p){
 74 d3df3087 2003-12-06 devnull 			qunlock(&mux->lk);
 75 d3df3087 2003-12-06 devnull 			p = _muxrecv(mux);
 76 d3df3087 2003-12-06 devnull 			if(p)
 77 0b22e9bd 2005-01-30 devnull 				tag = mux->gettag(mux, p) - mux->mintag;
 78 d3df3087 2003-12-06 devnull 			else
 79 d3df3087 2003-12-06 devnull 				tag = ~0;
 80 43db87f1 2004-12-27 devnull //print("mux tag %d\n", tag);
 81 d3df3087 2003-12-06 devnull 			qlock(&mux->lk);
 82 d3df3087 2003-12-06 devnull 			if(p == nil){	/* eof -- just give up and pass the buck */
 83 d3df3087 2003-12-06 devnull 				dequeue(mux, r);
 84 d3df3087 2003-12-06 devnull 				break;
 85 d3df3087 2003-12-06 devnull 			}
 86 d3df3087 2003-12-06 devnull 			/* hand packet to correct sleeper */
 87 d3df3087 2003-12-06 devnull 			if(tag < 0 || tag >= mux->mwait){
 88 d3df3087 2003-12-06 devnull 				fprint(2, "%s: bad rpc tag %ux\n", argv0, tag);
 89 d3df3087 2003-12-06 devnull 				/* must leak packet! don't know how to free it! */
 90 d3df3087 2003-12-06 devnull 				continue;
 91 d3df3087 2003-12-06 devnull 			}
 92 d3df3087 2003-12-06 devnull 			r2 = mux->wait[tag];
 93 d165fa68 2005-01-04 devnull 			if(r2 == nil || r2->prev == nil){
 94 43db87f1 2004-12-27 devnull 				fprint(2, "%s: bad rpc tag %ux (no one waiting on that tag)\n", argv0, tag);
 95 43db87f1 2004-12-27 devnull 				/* must leak packet! don't know how to free it! */
 96 43db87f1 2004-12-27 devnull 				continue;
 97 43db87f1 2004-12-27 devnull 			}	
 98 d3df3087 2003-12-06 devnull 			r2->p = p;
 99 e95a7088 2003-12-09 devnull 			dequeue(mux, r2);
100 d3df3087 2003-12-06 devnull 			rwakeup(&r2->r);
101 d3df3087 2003-12-06 devnull 		}
102 d3df3087 2003-12-06 devnull 		mux->muxer = 0;
103 d3df3087 2003-12-06 devnull 
104 d3df3087 2003-12-06 devnull 		/* if there is anyone else sleeping, wake them to mux */
105 d3df3087 2003-12-06 devnull 		if(mux->sleep.next != &mux->sleep)
106 d3df3087 2003-12-06 devnull 			rwakeup(&mux->sleep.next->r);
107 d3df3087 2003-12-06 devnull 	}
108 43db87f1 2004-12-27 devnull //print("finished %p\n", r);
109 d3df3087 2003-12-06 devnull 	p = r->p;
110 d165fa68 2005-01-04 devnull 	puttag(mux, r);
111 d3df3087 2003-12-06 devnull 	qunlock(&mux->lk);
112 a28c0548 2005-07-13 devnull 	if(p == nil)
113 a28c0548 2005-07-13 devnull 		werrstr("unexpected eof");
114 d3df3087 2003-12-06 devnull 	return p;
115 d3df3087 2003-12-06 devnull }
116 d3df3087 2003-12-06 devnull 
117 d3df3087 2003-12-06 devnull static void
118 d3df3087 2003-12-06 devnull enqueue(Mux *mux, Muxrpc *r)
119 d3df3087 2003-12-06 devnull {
120 d3df3087 2003-12-06 devnull 	r->next = mux->sleep.next;
121 d3df3087 2003-12-06 devnull 	r->prev = &mux->sleep;
122 d3df3087 2003-12-06 devnull 	r->next->prev = r;
123 d3df3087 2003-12-06 devnull 	r->prev->next = r;
124 d3df3087 2003-12-06 devnull }
125 d3df3087 2003-12-06 devnull 
126 d3df3087 2003-12-06 devnull static void
127 d3df3087 2003-12-06 devnull dequeue(Mux *mux, Muxrpc *r)
128 d3df3087 2003-12-06 devnull {
129 d3df3087 2003-12-06 devnull 	r->next->prev = r->prev;
130 d3df3087 2003-12-06 devnull 	r->prev->next = r->next;
131 d3df3087 2003-12-06 devnull 	r->prev = nil;
132 d3df3087 2003-12-06 devnull 	r->next = nil;
133 d3df3087 2003-12-06 devnull }
134 d3df3087 2003-12-06 devnull 
135 d3df3087 2003-12-06 devnull static int 
136 d3df3087 2003-12-06 devnull gettag(Mux *mux, Muxrpc *r)
137 d3df3087 2003-12-06 devnull {
138 ceb04770 2003-12-09 devnull 	int i, mw;
139 ceb04770 2003-12-09 devnull 	Muxrpc **w;
140 d3df3087 2003-12-06 devnull 
141 ceb04770 2003-12-09 devnull 	for(;;){
142 ceb04770 2003-12-09 devnull 		/* wait for a free tag */
143 ceb04770 2003-12-09 devnull 		while(mux->nwait == mux->mwait){
144 ceb04770 2003-12-09 devnull 			if(mux->mwait < mux->maxtag-mux->mintag){
145 ceb04770 2003-12-09 devnull 				mw = mux->mwait;
146 ceb04770 2003-12-09 devnull 				if(mw == 0)
147 ceb04770 2003-12-09 devnull 					mw = 1;
148 ceb04770 2003-12-09 devnull 				else
149 ceb04770 2003-12-09 devnull 					mw <<= 1;
150 ceb04770 2003-12-09 devnull 				w = realloc(mux->wait, mw*sizeof(w[0]));
151 ceb04770 2003-12-09 devnull 				if(w == nil)
152 ceb04770 2003-12-09 devnull 					return -1;
153 e95a7088 2003-12-09 devnull 				memset(w+mux->mwait, 0, (mw-mux->mwait)*sizeof(w[0]));
154 ceb04770 2003-12-09 devnull 				mux->wait = w;
155 ceb04770 2003-12-09 devnull 				mux->freetag = mux->mwait;
156 ceb04770 2003-12-09 devnull 				mux->mwait = mw;
157 ceb04770 2003-12-09 devnull 				break;
158 ceb04770 2003-12-09 devnull 			}
159 ceb04770 2003-12-09 devnull 			rsleep(&mux->tagrend);
160 d3df3087 2003-12-06 devnull 		}
161 ceb04770 2003-12-09 devnull 
162 ceb04770 2003-12-09 devnull 		i=mux->freetag;
163 ceb04770 2003-12-09 devnull 		if(mux->wait[i] == 0)
164 ceb04770 2003-12-09 devnull 			goto Found;
165 ceb04770 2003-12-09 devnull 		for(; i<mux->mwait; i++)
166 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
167 ceb04770 2003-12-09 devnull 				goto Found;
168 ceb04770 2003-12-09 devnull 		for(i=0; i<mux->freetag; i++)
169 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
170 ceb04770 2003-12-09 devnull 				goto Found;
171 ceb04770 2003-12-09 devnull 		/* should not fall out of while without free tag */
172 ceb04770 2003-12-09 devnull 		fprint(2, "libfs: nwait botch\n");
173 ceb04770 2003-12-09 devnull 		abort();
174 ceb04770 2003-12-09 devnull 	}
175 ceb04770 2003-12-09 devnull 
176 ceb04770 2003-12-09 devnull Found:
177 ceb04770 2003-12-09 devnull 	mux->nwait++;
178 ceb04770 2003-12-09 devnull 	mux->wait[i] = r;
179 ceb04770 2003-12-09 devnull 	r->tag = i+mux->mintag;
180 0b22e9bd 2005-01-30 devnull 	return r->tag;
181 d3df3087 2003-12-06 devnull }
182 d3df3087 2003-12-06 devnull 
183 d3df3087 2003-12-06 devnull static void
184 d3df3087 2003-12-06 devnull puttag(Mux *mux, Muxrpc *r)
185 d3df3087 2003-12-06 devnull {
186 ceb04770 2003-12-09 devnull 	int i;
187 ceb04770 2003-12-09 devnull 
188 ceb04770 2003-12-09 devnull 	i = r->tag - mux->mintag;
189 ceb04770 2003-12-09 devnull 	assert(mux->wait[i] == r);
190 ceb04770 2003-12-09 devnull 	mux->wait[i] = nil;
191 d3df3087 2003-12-06 devnull 	mux->nwait--;
192 ceb04770 2003-12-09 devnull 	mux->freetag = i;
193 d3df3087 2003-12-06 devnull 	rwakeup(&mux->tagrend);
194 ceb04770 2003-12-09 devnull 	free(r);
195 d3df3087 2003-12-06 devnull }