1 #include <u.h>
2 #include <libc.h>
3 #include <thread.h>
4 #include <9pclient.h>
5 #include "acme.h"
6 
7 extern int debug;
8 
9 #define dprint if(debug>1)print
10 
11 typedef struct Waitreq Waitreq;
12 struct Waitreq
13 {
14 	int pid;
15 	Channel *c;
16 };
17 
18 /*
19  * watch the exiting children
20  */
21 Channel *twaitchan;	/* chan(Waitreq) */
22 void
23 waitthread(void *v)
24 {
25 	Alt a[3];
26 	Waitmsg *w, **wq;
27 	Waitreq *rq, r;
28 	int i, nrq, nwq;
29 
30 	threadsetname("waitthread");
31 	a[0].c = threadwaitchan();
32 	a[0].v = &w;
33 	a[0].op = CHANRCV;
34 	a[1].c = twaitchan;
35 	a[1].v = &r;
36 	a[1].op = CHANRCV;
37 	a[2].op = CHANEND;
38 
39 	nrq = 0;
40 	nwq = 0;
41 	rq = nil;
42 	wq = nil;
43 	dprint("wait: start\n");
44 	for(;;){
45 	cont2:;
46 		dprint("wait: alt\n");
47 		switch(alt(a)){
48 		case 0:
49 			dprint("wait: pid %d exited\n", w->pid);
50 			for(i=0; i<nrq; i++){
51 				if(rq[i].pid == w->pid){
52 					dprint("wait: match with rq chan %p\n", rq[i].c);
53 					sendp(rq[i].c, w);
54 					rq[i] = rq[--nrq];
55 					goto cont2;
56 				}
57 			}
58 			if(i == nrq){
59 				dprint("wait: queueing waitmsg\n");
60 				wq = erealloc(wq, (nwq+1)*sizeof(wq[0]));
61 				wq[nwq++] = w;
62 			}
63 			break;
64 
65 		case 1:
66 			dprint("wait: req for pid %d chan %p\n", r.pid, r.c);
67 			for(i=0; i<nwq; i++){
68 				if(w->pid == r.pid){
69 					dprint("wait: match with waitmsg\n");
70 					sendp(r.c, w);
71 					wq[i] = wq[--nwq];
72 					goto cont2;
73 				}
74 			}
75 			if(i == nwq){
76 				dprint("wait: queueing req\n");
77 				rq = erealloc(rq, (nrq+1)*sizeof(rq[0]));
78 				rq[nrq] = r;
79 				dprint("wait: queueing req pid %d chan %p\n", rq[nrq].pid, rq[nrq].c);
80 				nrq++;
81 			}
82 			break;
83 		}
84 	}
85 }
86 
87 Waitmsg*
88 twaitfor(int pid)
89 {
90 	Waitreq r;
91 	Waitmsg *w;
92 
93 	r.pid = pid;
94 	r.c = chancreate(sizeof(Waitmsg*), 1);
95 	send(twaitchan, &r);
96 	w = recvp(r.c);
97 	chanfree(r.c);
98 	return w;
99 }
100 
101 int
102 twait(int pid)
103 {
104 	int x;
105 	Waitmsg *w;
106 
107 	w = twaitfor(pid);
108 	x = w->msg[0] != 0 ? -1 : 0;
109 	free(w);
110 	return x;
111 }
112 
113 void
114 twaitinit(void)
115 {
116 	threadwaitchan();	/* allocate it before returning */
117 	twaitchan = chancreate(sizeof(Waitreq), 10);
118 	threadcreate(waitthread, nil, 128*1024);
119 }