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 43db87f1 2004-12-27 devnull 	/* assign the tag, add selves to response queue */
 43 ceb04770 2003-12-09 devnull 	qlock(&mux->lk);
 44 d3df3087 2003-12-06 devnull 	tag = gettag(mux, r);
 45 43db87f1 2004-12-27 devnull //print("gettag %p %d\n", r, tag);
 46 43db87f1 2004-12-27 devnull 	enqueue(mux, r);
 47 ceb04770 2003-12-09 devnull 	qunlock(&mux->lk);
 48 43db87f1 2004-12-27 devnull 
 49 43db87f1 2004-12-27 devnull 	/* actually send the packet */
 50 ceb04770 2003-12-09 devnull 	if(tag < 0 || mux->settag(mux, tx, tag) < 0 || _muxsend(mux, tx) < 0){
 51 ceb04770 2003-12-09 devnull 		qlock(&mux->lk);
 52 d3df3087 2003-12-06 devnull 		puttag(mux, r);
 53 ceb04770 2003-12-09 devnull 		qunlock(&mux->lk);
 54 d3df3087 2003-12-06 devnull 		return nil;
 55 d3df3087 2003-12-06 devnull 	}
 56 d3df3087 2003-12-06 devnull 
 57 d3df3087 2003-12-06 devnull 	qlock(&mux->lk);
 58 d3df3087 2003-12-06 devnull 	/* wait for our packet */
 59 c6687d45 2004-09-21 devnull 	while(mux->muxer && !r->p){
 60 d3df3087 2003-12-06 devnull 		rsleep(&r->r);
 61 c6687d45 2004-09-21 devnull 	}
 62 d3df3087 2003-12-06 devnull 
 63 d3df3087 2003-12-06 devnull 	/* if not done, there's no muxer: start muxing */
 64 d3df3087 2003-12-06 devnull 	if(!r->p){
 65 d3df3087 2003-12-06 devnull 		if(mux->muxer)
 66 d3df3087 2003-12-06 devnull 			abort();
 67 d3df3087 2003-12-06 devnull 		mux->muxer = 1;
 68 d3df3087 2003-12-06 devnull 		while(!r->p){
 69 d3df3087 2003-12-06 devnull 			qunlock(&mux->lk);
 70 d3df3087 2003-12-06 devnull 			p = _muxrecv(mux);
 71 d3df3087 2003-12-06 devnull 			if(p)
 72 d3df3087 2003-12-06 devnull 				tag = mux->gettag(mux, p);
 73 d3df3087 2003-12-06 devnull 			else
 74 d3df3087 2003-12-06 devnull 				tag = ~0;
 75 43db87f1 2004-12-27 devnull //print("mux tag %d\n", tag);
 76 d3df3087 2003-12-06 devnull 			qlock(&mux->lk);
 77 d3df3087 2003-12-06 devnull 			if(p == nil){	/* eof -- just give up and pass the buck */
 78 d3df3087 2003-12-06 devnull 				dequeue(mux, r);
 79 d3df3087 2003-12-06 devnull 				break;
 80 d3df3087 2003-12-06 devnull 			}
 81 d3df3087 2003-12-06 devnull 			/* hand packet to correct sleeper */
 82 d3df3087 2003-12-06 devnull 			if(tag < 0 || tag >= mux->mwait){
 83 d3df3087 2003-12-06 devnull 				fprint(2, "%s: bad rpc tag %ux\n", argv0, tag);
 84 d3df3087 2003-12-06 devnull 				/* must leak packet! don't know how to free it! */
 85 d3df3087 2003-12-06 devnull 				continue;
 86 d3df3087 2003-12-06 devnull 			}
 87 d3df3087 2003-12-06 devnull 			r2 = mux->wait[tag];
 88 43db87f1 2004-12-27 devnull 			if(r2 == nil){
 89 43db87f1 2004-12-27 devnull 				fprint(2, "%s: bad rpc tag %ux (no one waiting on that tag)\n", argv0, tag);
 90 43db87f1 2004-12-27 devnull 				/* must leak packet! don't know how to free it! */
 91 43db87f1 2004-12-27 devnull 				continue;
 92 43db87f1 2004-12-27 devnull 			}	
 93 d3df3087 2003-12-06 devnull 			r2->p = p;
 94 e95a7088 2003-12-09 devnull 			dequeue(mux, r2);
 95 43db87f1 2004-12-27 devnull 			puttag(mux, r2);
 96 d3df3087 2003-12-06 devnull 			rwakeup(&r2->r);
 97 d3df3087 2003-12-06 devnull 		}
 98 d3df3087 2003-12-06 devnull 		mux->muxer = 0;
 99 d3df3087 2003-12-06 devnull 
100 d3df3087 2003-12-06 devnull 		/* if there is anyone else sleeping, wake them to mux */
101 d3df3087 2003-12-06 devnull 		if(mux->sleep.next != &mux->sleep)
102 d3df3087 2003-12-06 devnull 			rwakeup(&mux->sleep.next->r);
103 d3df3087 2003-12-06 devnull 	}
104 43db87f1 2004-12-27 devnull //print("finished %p\n", r);
105 d3df3087 2003-12-06 devnull 	p = r->p;
106 d3df3087 2003-12-06 devnull 	qunlock(&mux->lk);
107 d3df3087 2003-12-06 devnull 	return p;
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 enqueue(Mux *mux, Muxrpc *r)
112 d3df3087 2003-12-06 devnull {
113 d3df3087 2003-12-06 devnull 	r->next = mux->sleep.next;
114 d3df3087 2003-12-06 devnull 	r->prev = &mux->sleep;
115 d3df3087 2003-12-06 devnull 	r->next->prev = r;
116 d3df3087 2003-12-06 devnull 	r->prev->next = r;
117 d3df3087 2003-12-06 devnull }
118 d3df3087 2003-12-06 devnull 
119 d3df3087 2003-12-06 devnull static void
120 d3df3087 2003-12-06 devnull dequeue(Mux *mux, Muxrpc *r)
121 d3df3087 2003-12-06 devnull {
122 d3df3087 2003-12-06 devnull 	r->next->prev = r->prev;
123 d3df3087 2003-12-06 devnull 	r->prev->next = r->next;
124 d3df3087 2003-12-06 devnull 	r->prev = nil;
125 d3df3087 2003-12-06 devnull 	r->next = nil;
126 d3df3087 2003-12-06 devnull }
127 d3df3087 2003-12-06 devnull 
128 d3df3087 2003-12-06 devnull static int 
129 d3df3087 2003-12-06 devnull gettag(Mux *mux, Muxrpc *r)
130 d3df3087 2003-12-06 devnull {
131 ceb04770 2003-12-09 devnull 	int i, mw;
132 ceb04770 2003-12-09 devnull 	Muxrpc **w;
133 d3df3087 2003-12-06 devnull 
134 ceb04770 2003-12-09 devnull 	for(;;){
135 ceb04770 2003-12-09 devnull 		/* wait for a free tag */
136 ceb04770 2003-12-09 devnull 		while(mux->nwait == mux->mwait){
137 ceb04770 2003-12-09 devnull 			if(mux->mwait < mux->maxtag-mux->mintag){
138 ceb04770 2003-12-09 devnull 				mw = mux->mwait;
139 ceb04770 2003-12-09 devnull 				if(mw == 0)
140 ceb04770 2003-12-09 devnull 					mw = 1;
141 ceb04770 2003-12-09 devnull 				else
142 ceb04770 2003-12-09 devnull 					mw <<= 1;
143 ceb04770 2003-12-09 devnull 				w = realloc(mux->wait, mw*sizeof(w[0]));
144 ceb04770 2003-12-09 devnull 				if(w == nil)
145 ceb04770 2003-12-09 devnull 					return -1;
146 e95a7088 2003-12-09 devnull 				memset(w+mux->mwait, 0, (mw-mux->mwait)*sizeof(w[0]));
147 ceb04770 2003-12-09 devnull 				mux->wait = w;
148 ceb04770 2003-12-09 devnull 				mux->freetag = mux->mwait;
149 ceb04770 2003-12-09 devnull 				mux->mwait = mw;
150 ceb04770 2003-12-09 devnull 				break;
151 ceb04770 2003-12-09 devnull 			}
152 ceb04770 2003-12-09 devnull 			rsleep(&mux->tagrend);
153 d3df3087 2003-12-06 devnull 		}
154 ceb04770 2003-12-09 devnull 
155 ceb04770 2003-12-09 devnull 		i=mux->freetag;
156 ceb04770 2003-12-09 devnull 		if(mux->wait[i] == 0)
157 ceb04770 2003-12-09 devnull 			goto Found;
158 ceb04770 2003-12-09 devnull 		for(; i<mux->mwait; i++)
159 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
160 ceb04770 2003-12-09 devnull 				goto Found;
161 ceb04770 2003-12-09 devnull 		for(i=0; i<mux->freetag; i++)
162 ceb04770 2003-12-09 devnull 			if(mux->wait[i] == 0)
163 ceb04770 2003-12-09 devnull 				goto Found;
164 ceb04770 2003-12-09 devnull 		/* should not fall out of while without free tag */
165 ceb04770 2003-12-09 devnull 		fprint(2, "libfs: nwait botch\n");
166 ceb04770 2003-12-09 devnull 		abort();
167 ceb04770 2003-12-09 devnull 	}
168 ceb04770 2003-12-09 devnull 
169 ceb04770 2003-12-09 devnull Found:
170 ceb04770 2003-12-09 devnull 	mux->nwait++;
171 ceb04770 2003-12-09 devnull 	mux->wait[i] = r;
172 ceb04770 2003-12-09 devnull 	r->tag = i+mux->mintag;
173 ceb04770 2003-12-09 devnull 	return i;
174 d3df3087 2003-12-06 devnull }
175 d3df3087 2003-12-06 devnull 
176 d3df3087 2003-12-06 devnull static void
177 d3df3087 2003-12-06 devnull puttag(Mux *mux, Muxrpc *r)
178 d3df3087 2003-12-06 devnull {
179 ceb04770 2003-12-09 devnull 	int i;
180 ceb04770 2003-12-09 devnull 
181 ceb04770 2003-12-09 devnull 	i = r->tag - mux->mintag;
182 ceb04770 2003-12-09 devnull 	assert(mux->wait[i] == r);
183 ceb04770 2003-12-09 devnull 	mux->wait[i] = nil;
184 d3df3087 2003-12-06 devnull 	mux->nwait--;
185 ceb04770 2003-12-09 devnull 	mux->freetag = i;
186 d3df3087 2003-12-06 devnull 	rwakeup(&mux->tagrend);
187 ceb04770 2003-12-09 devnull 	free(r);
188 d3df3087 2003-12-06 devnull }