1 #include <u.h>
2 #include <signal.h>
3 #include <errno.h>
4 #include "threadimpl.h"
5 
6 //static Thread	*runthread(Proc*);
7 
8 static char *_psstate[] = {
9 	"Dead",
10 	"Running",
11 	"Ready",
12 	"Rendezvous",
13 };
14 
15 static char*
16 psstate(int s)
17 {
18 	if(s < 0 || s >= nelem(_psstate))
19 		return "unknown";
20 	return _psstate[s];
21 }
22 
23 void
24 _schedinit(void *arg)
25 {
26 	Proc *p;
27 	Thread *t;
28 	extern void ignusr1(void), _threaddie(int);
29 	ignusr1();
30 	signal(SIGTERM, _threaddie);
31   
32 	p = arg;
33 	lock(&p->lock);
34 	p->pid = _threadgetpid();
35 	_threadsetproc(p);
36 	unlock(&p->lock);
37 	while(_setlabel(&p->sched))
38 		;
39 	_threaddebug(DBGSCHED, "top of schedinit, _threadexitsallstatus=%p", _threadexitsallstatus);
40 	if(_threadexitsallstatus)
41 		exits(_threadexitsallstatus);
42 	lock(&p->lock);
43 	if((t=p->thread) != nil){
44 		p->thread = nil;
45 		if(t->moribund){
46 			if(t->moribund != 1)
47 				fprint(2, "moribund %d\n", t->moribund);
48 			assert(t->moribund == 1);
49 			t->state = Dead;
50 			if(t->prevt)
51 				t->prevt->nextt = t->nextt;
52 			else
53 				p->threads.head = t->nextt;
54 			if(t->nextt)
55 				t->nextt->prevt = t->prevt;
56 			else
57 				p->threads.tail = t->prevt;
58 			unlock(&p->lock);
59 			if(t->inrendez){
60 				_threadflagrendez(t);
61 				_threadbreakrendez();
62 			}
63 			_stackfree(t->stk);
64 			free(t->cmdname);
65 			free(t);	/* XXX how do we know there are no references? */
66 			p->nthreads--;
67 			t = nil;
68 			_sched();
69 		}
70 /*
71 		if(p->needexec){
72 			t->ret = _schedexec(&p->exec);
73 			p->needexec = 0;
74 		}
75 */
76 		if(p->newproc){
77 			t->ret = _schedfork(p->newproc);
78 			if(t->ret < 0){
79 //fprint(2, "_schedfork: %r\n");
80 				abort();
81 }
82 			p->newproc = nil;
83 		}
84 		t->state = t->nextstate;
85 		if(t->state == Ready)
86 			_threadready(t);
87 	}
88 	unlock(&p->lock);
89 	_sched();
90 }
91 
92 static Thread*
93 runthread(Proc *p)
94 {
95 	Channel *c;
96 	Thread *t;
97 	Tqueue *q;
98 	Waitmsg *w;
99 	int e, sent;
100 
101 	if(p->nthreads==0 || (p->nthreads==1 && p->idle))
102 		return nil;
103 	q = &p->ready;
104 relock:
105 	lock(&p->readylock);
106 	if(q->head == nil){
107 		e = errno;
108 		if((c = _threadwaitchan) != nil){
109 			if(c->n <= c->s){
110 				sent = 0;
111 				for(;;){
112 					if((w = p->waitmsg) != nil)
113 						p->waitmsg = nil;
114 					else
115 						w = waitnohang();
116 					if(w == nil)
117 						break;
118 					if(sent == 0){
119 						unlock(&p->readylock);
120 						sent = 1;
121 					}
122 					if(nbsendp(c, w) != 1)
123 						break;
124 				}
125 				p->waitmsg = w;
126 				if(sent)
127 					goto relock;
128 			}
129 		}else{
130 			while((w = waitnohang()) != nil)
131 				free(w);
132 		}
133 		errno = e;
134 		if(p->idle){
135 			if(p->idle->state != Ready){
136 				fprint(2, "everyone is asleep\n");
137 				exits("everyone is asleep");
138 			}
139 			unlock(&p->readylock);
140 			_threaddebug(DBGSCHED, "running idle thread", p->nthreads);
141 			return p->idle;
142 		}
143 
144 		_threaddebug(DBGSCHED, "sleeping for more work (%d threads)", p->nthreads);
145 		q->asleep = 1;
146 		unlock(&p->readylock);
147 		while(rendezvous((ulong)q, 0) == ~0){
148 			if(_threadexitsallstatus)
149 				exits(_threadexitsallstatus);
150 		}
151 		/* lock picked up from _threadready */
152 	}
153 	t = q->head;
154 	q->head = t->next;
155 	unlock(&p->readylock);
156 	return t;
157 }
158 
159 void
160 _sched(void)
161 {
162 	Proc *p;
163 	Thread *t;
164 
165 Resched:
166 	p = _threadgetproc();
167 //fprint(2, "p %p\n", p);
168 	if((t = p->thread) != nil){
169 		if((ulong)&p < (ulong)t->stk+512){	/* stack overflow waiting to happen */
170 			fprint(2, "stack overflow: stack at %lux, limit at %lux\n", (ulong)&p, (ulong)t->stk);
171 			abort();
172 		}
173 	//	_threaddebug(DBGSCHED, "pausing, state=%s set %p goto %p",
174 	//		psstate(t->state), &t->sched, &p->sched);
175 		if(_setlabel(&t->sched)==0)
176 			_gotolabel(&p->sched);
177 		_threadstacklimit(t->stk);
178 		return;
179 	}else{
180 		t = runthread(p);
181 		if(t == nil){
182 			_threaddebug(DBGSCHED, "all threads gone; exiting");
183 			_threaddelproc();
184 			_schedexit(p);
185 		}
186 		_threaddebug(DBGSCHED, "running %d.%d", t->proc->pid, t->id);
187 		p->thread = t;
188 		if(t->moribund){
189 			_threaddebug(DBGSCHED, "%d.%d marked to die");
190 			goto Resched;
191 		}
192 		t->state = Running;
193 		t->nextstate = Ready;
194 		_gotolabel(&t->sched);
195 	}
196 }
197 
198 long
199 threadstack(void)
200 {
201 	Proc *p;
202 	Thread *t;
203 
204 	p = _threadgetproc();
205 	t = p->thread;
206 	return (ulong)&p - (ulong)t->stk;
207 }
208 
209 void
210 _threadready(Thread *t)
211 {
212 	Tqueue *q;
213 
214 	if(t == t->proc->idle){
215 		_threaddebug(DBGSCHED, "idle thread is ready");
216 		return;
217 	}
218 
219 	assert(t->state == Ready);
220 	_threaddebug(DBGSCHED, "readying %d.%d", t->proc->pid, t->id);
221 	q = &t->proc->ready;
222 	lock(&t->proc->readylock);
223 	t->next = nil;
224 	if(q->head==nil)
225 		q->head = t;
226 	else
227 		q->tail->next = t;
228 	q->tail = t;
229 	if(q->asleep){
230 		assert(q->asleep == 1);
231 		q->asleep = 0;
232 		/* lock passes to runthread */
233 		_threaddebug(DBGSCHED, "waking process %d", t->proc->pid);
234 		while(rendezvous((ulong)q, 0) == ~0){
235 			if(_threadexitsallstatus)
236 				exits(_threadexitsallstatus);
237 		}
238 	}else
239 		unlock(&t->proc->readylock);
240 }
241 
242 void
243 _threadidle(void)
244 {
245 	Tqueue *q;
246 	Thread *t, *idle;
247 	Proc *p;
248 
249 	p = _threadgetproc();
250 	q = &p->ready;
251 	lock(&p->readylock);
252 	assert(q->tail);
253 	idle = q->tail;
254 	if(q->head == idle){
255 		q->head = nil;
256 		q->tail = nil;
257 	}else{
258 		for(t=q->head; t->next!=q->tail; t=t->next)
259 			;
260 		t->next = nil;
261 		q->tail = t;
262 	}
263 	p->idle = idle;
264 	_threaddebug(DBGSCHED, "p->idle is %d\n", idle->id);
265 	unlock(&p->readylock);
266 }
267 
268 void
269 yield(void)
270 {
271 	_sched();
272 }
273 
274 void
275 threadstatus(void)
276 {
277 	Proc *p;
278 	Thread *t;
279 
280 	p = _threadgetproc();
281 	for(t=p->threads.head; t; t=t->nextt)
282 		fprint(2, "[%3d] %s userpc=%lux\n",
283 			t->id, psstate(t->state), t->userpc);
284 }
285