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