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 d3df3087 2003-12-06 devnull 	mux->tagrend.l = &mux->lk;
 23 d3df3087 2003-12-06 devnull 	mux->sleep.next = &mux->sleep;
 24 d3df3087 2003-12-06 devnull 	mux->sleep.prev = &mux->sleep;
 25 d3df3087 2003-12-06 devnull }
 26 d3df3087 2003-12-06 devnull 
 27 d3df3087 2003-12-06 devnull void*
 28 d3df3087 2003-12-06 devnull muxrpc(Mux *mux, void *tx)
 29 d3df3087 2003-12-06 devnull {
 30 ceb04770 2003-12-09 devnull 	int tag;
 31 d3df3087 2003-12-06 devnull 	Muxrpc *r, *r2;
 32 d3df3087 2003-12-06 devnull 	void *p;
 33 d3df3087 2003-12-06 devnull 
 34 d3df3087 2003-12-06 devnull 	/* must malloc because stack could be private */
 35 d3df3087 2003-12-06 devnull 	r = mallocz(sizeof(Muxrpc), 1);
 36 d3df3087 2003-12-06 devnull 	if(r == nil)
 37 d3df3087 2003-12-06 devnull 		return nil;
 38 d3df3087 2003-12-06 devnull 	r->r.l = &mux->lk;
 39 d3df3087 2003-12-06 devnull 
 40 d3df3087 2003-12-06 devnull 	/* assign the tag */
 41 ceb04770 2003-12-09 devnull 	qlock(&mux->lk);
 42 d3df3087 2003-12-06 devnull 	tag = gettag(mux, r);
 43 ceb04770 2003-12-09 devnull 	qunlock(&mux->lk);
 44 ceb04770 2003-12-09 devnull 	if(tag < 0 || mux->settag(mux, tx, tag) < 0 || _muxsend(mux, tx) < 0){
 45 ceb04770 2003-12-09 devnull 		qlock(&mux->lk);
 46 d3df3087 2003-12-06 devnull 		puttag(mux, r);
 47 ceb04770 2003-12-09 devnull 		qunlock(&mux->lk);
 48 d3df3087 2003-12-06 devnull 		return nil;
 49 d3df3087 2003-12-06 devnull 	}
 50 d3df3087 2003-12-06 devnull 
 51 d3df3087 2003-12-06 devnull 	/* add ourselves to sleep queue */
 52 d3df3087 2003-12-06 devnull 	qlock(&mux->lk);
 53 d3df3087 2003-12-06 devnull 	enqueue(mux, r);
 54 d3df3087 2003-12-06 devnull 
 55 d3df3087 2003-12-06 devnull 	/* wait for our packet */
 56 d3df3087 2003-12-06 devnull 	while(mux->muxer && !r->p)
 57 d3df3087 2003-12-06 devnull 		rsleep(&r->r);
 58 d3df3087 2003-12-06 devnull 
 59 d3df3087 2003-12-06 devnull 	/* if not done, there's no muxer: start muxing */
 60 d3df3087 2003-12-06 devnull 	if(!r->p){
 61 d3df3087 2003-12-06 devnull 		if(mux->muxer)
 62 d3df3087 2003-12-06 devnull 			abort();
 63 d3df3087 2003-12-06 devnull 		mux->muxer = 1;
 64 d3df3087 2003-12-06 devnull 		while(!r->p){
 65 d3df3087 2003-12-06 devnull 			qunlock(&mux->lk);
 66 d3df3087 2003-12-06 devnull 			p = _muxrecv(mux);
 67 d3df3087 2003-12-06 devnull 			if(p)
 68 d3df3087 2003-12-06 devnull 				tag = mux->gettag(mux, p);
 69 d3df3087 2003-12-06 devnull 			else
 70 d3df3087 2003-12-06 devnull 				tag = ~0;
 71 d3df3087 2003-12-06 devnull 			qlock(&mux->lk);
 72 d3df3087 2003-12-06 devnull 			if(p == nil){	/* eof -- just give up and pass the buck */
 73 d3df3087 2003-12-06 devnull 				dequeue(mux, r);
 74 d3df3087 2003-12-06 devnull 				break;
 75 d3df3087 2003-12-06 devnull 			}
 76 d3df3087 2003-12-06 devnull 			/* hand packet to correct sleeper */
 77 d3df3087 2003-12-06 devnull 			if(tag < 0 || tag >= mux->mwait){
 78 d3df3087 2003-12-06 devnull 				fprint(2, "%s: bad rpc tag %ux\n", argv0, tag);
 79 d3df3087 2003-12-06 devnull 				/* must leak packet! don't know how to free it! */
 80 d3df3087 2003-12-06 devnull 				continue;
 81 d3df3087 2003-12-06 devnull 			}
 82 d3df3087 2003-12-06 devnull 			r2 = mux->wait[tag];
 83 d3df3087 2003-12-06 devnull 			r2->p = p;
 84 e95a7088 2003-12-09 devnull 			dequeue(mux, r2);
 85 d3df3087 2003-12-06 devnull 			rwakeup(&r2->r);
 86 d3df3087 2003-12-06 devnull 		}
 87 d3df3087 2003-12-06 devnull 		mux->muxer = 0;
 88 d3df3087 2003-12-06 devnull 
 89 d3df3087 2003-12-06 devnull 		/* if there is anyone else sleeping, wake them to mux */
 90 d3df3087 2003-12-06 devnull 		if(mux->sleep.next != &mux->sleep)
 91 d3df3087 2003-12-06 devnull 			rwakeup(&mux->sleep.next->r);
 92 d3df3087 2003-12-06 devnull 	}
 93 d3df3087 2003-12-06 devnull 	p = r->p;
 94 d3df3087 2003-12-06 devnull 	puttag(mux, r);
 95 d3df3087 2003-12-06 devnull 	qunlock(&mux->lk);
 96 d3df3087 2003-12-06 devnull 	return p;
 97 d3df3087 2003-12-06 devnull }
 98 d3df3087 2003-12-06 devnull 
 99 d3df3087 2003-12-06 devnull static void
100 d3df3087 2003-12-06 devnull enqueue(Mux *mux, Muxrpc *r)
101 d3df3087 2003-12-06 devnull {
102 d3df3087 2003-12-06 devnull 	r->next = mux->sleep.next;
103 d3df3087 2003-12-06 devnull 	r->prev = &mux->sleep;
104 d3df3087 2003-12-06 devnull 	r->next->prev = r;
105 d3df3087 2003-12-06 devnull 	r->prev->next = r;
106 d3df3087 2003-12-06 devnull }
107 d3df3087 2003-12-06 devnull 
108 d3df3087 2003-12-06 devnull static void
109 d3df3087 2003-12-06 devnull dequeue(Mux *mux, Muxrpc *r)
110 d3df3087 2003-12-06 devnull {
111 d3df3087 2003-12-06 devnull 	r->next->prev = r->prev;
112 d3df3087 2003-12-06 devnull 	r->prev->next = r->next;
113 d3df3087 2003-12-06 devnull 	r->prev = nil;
114 d3df3087 2003-12-06 devnull 	r->next = nil;
115 d3df3087 2003-12-06 devnull }
116 d3df3087 2003-12-06 devnull 
117 d3df3087 2003-12-06 devnull static int 
118 d3df3087 2003-12-06 devnull gettag(Mux *mux, Muxrpc *r)
119 d3df3087 2003-12-06 devnull {
120 ceb04770 2003-12-09 devnull 	int i, mw;
121 ceb04770 2003-12-09 devnull 	Muxrpc **w;
122 d3df3087 2003-12-06 devnull 
123 ceb04770 2003-12-09 devnull 	for(;;){
124 ceb04770 2003-12-09 devnull 		/* wait for a free tag */
125 ceb04770 2003-12-09 devnull 		while(mux->nwait == mux->mwait){
126 ceb04770 2003-12-09 devnull 			if(mux->mwait < mux->maxtag-mux->mintag){
127 ceb04770 2003-12-09 devnull 				mw = mux->mwait;
128 ceb04770 2003-12-09 devnull 				if(mw == 0)
129 ceb04770 2003-12-09 devnull 					mw = 1;
130 ceb04770 2003-12-09 devnull 				else
131 ceb04770 2003-12-09 devnull 					mw <<= 1;
132 ceb04770 2003-12-09 devnull 				w = realloc(mux->wait, mw*sizeof(w[0]));
133 ceb04770 2003-12-09 devnull 				if(w == nil)
134 ceb04770 2003-12-09 devnull 					return -1;
135 e95a7088 2003-12-09 devnull 				memset(w+mux->mwait, 0, (mw-mux->mwait)*sizeof(w[0]));
136 ceb04770 2003-12-09 devnull 				mux->wait = w;
137 ceb04770 2003-12-09 devnull 				mux->freetag = mux->mwait;
138 ceb04770 2003-12-09 devnull 				mux->mwait = mw;
139 ceb04770 2003-12-09 devnull 				break;
140 ceb04770 2003-12-09 devnull 			}
141 ceb04770 2003-12-09 devnull 			rsleep(&mux->tagrend);
142 d3df3087 2003-12-06 devnull 		}
143 ceb04770 2003-12-09 devnull 
144 ceb04770 2003-12-09 devnull 		i=mux->freetag;
145 ceb04770 2003-12-09 devnull 		if(mux->wait[i] == 0)
146 ceb04770 2003-12-09 devnull 			goto Found;
147 ceb04770 2003-12-09 devnull 		for(; i<mux->mwait; i++)
148 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
149 ceb04770 2003-12-09 devnull 				goto Found;
150 ceb04770 2003-12-09 devnull 		for(i=0; i<mux->freetag; i++)
151 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
152 ceb04770 2003-12-09 devnull 				goto Found;
153 ceb04770 2003-12-09 devnull 		/* should not fall out of while without free tag */
154 ceb04770 2003-12-09 devnull 		fprint(2, "libfs: nwait botch\n");
155 ceb04770 2003-12-09 devnull 		abort();
156 ceb04770 2003-12-09 devnull 	}
157 ceb04770 2003-12-09 devnull 
158 ceb04770 2003-12-09 devnull Found:
159 ceb04770 2003-12-09 devnull 	mux->nwait++;
160 ceb04770 2003-12-09 devnull 	mux->wait[i] = r;
161 ceb04770 2003-12-09 devnull 	r->tag = i+mux->mintag;
162 ceb04770 2003-12-09 devnull 	return i;
163 d3df3087 2003-12-06 devnull }
164 d3df3087 2003-12-06 devnull 
165 d3df3087 2003-12-06 devnull static void
166 d3df3087 2003-12-06 devnull puttag(Mux *mux, Muxrpc *r)
167 d3df3087 2003-12-06 devnull {
168 ceb04770 2003-12-09 devnull 	int i;
169 ceb04770 2003-12-09 devnull 
170 ceb04770 2003-12-09 devnull 	i = r->tag - mux->mintag;
171 ceb04770 2003-12-09 devnull 	assert(mux->wait[i] == r);
172 ceb04770 2003-12-09 devnull 	mux->wait[i] = nil;
173 d3df3087 2003-12-06 devnull 	mux->nwait--;
174 ceb04770 2003-12-09 devnull 	mux->freetag = i;
175 d3df3087 2003-12-06 devnull 	rwakeup(&mux->tagrend);
176 ceb04770 2003-12-09 devnull 	free(r);
177 d3df3087 2003-12-06 devnull }