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 needstack(int howmuch)
161 {
162 	Proc *p;
163 	Thread *t;
164 
165 	p = _threadgetproc();
166 	if(p == nil || (t=p->thread) == nil)
167 		return;
168 	if((ulong)&howmuch < (ulong)t->stk+howmuch){	/* stack overflow waiting to happen */
169 		fprint(2, "stack overflow: stack at 0x%lux, limit at 0x%lux, need 0x%lux\n", (ulong)&p, (ulong)t->stk, howmuch);
170 		abort();
171 	}
172 }
173 
174 void
175 _sched(void)
176 {
177 	Proc *p;
178 	Thread *t;
179 
180 Resched:
181 	p = _threadgetproc();
182 //fprint(2, "p %p\n", p);
183 	if((t = p->thread) != nil){
184 		needstack(512);
185 	//	_threaddebug(DBGSCHED, "pausing, state=%s set %p goto %p",
186 	//		psstate(t->state), &t->sched, &p->sched);
187 		if(_setlabel(&t->sched)==0)
188 			_gotolabel(&p->sched);
189 		_threadstacklimit(t->stk);
190 		return;
191 	}else{
192 		t = runthread(p);
193 		if(t == nil){
194 			_threaddebug(DBGSCHED, "all threads gone; exiting");
195 			_threaddelproc();
196 			_schedexit(p);
197 		}
198 		_threaddebug(DBGSCHED, "running %d.%d", t->proc->pid, t->id);
199 		p->thread = t;
200 		if(t->moribund){
201 			_threaddebug(DBGSCHED, "%d.%d marked to die");
202 			goto Resched;
203 		}
204 		t->state = Running;
205 		t->nextstate = Ready;
206 		_gotolabel(&t->sched);
207 	}
208 }
209 
210 long
211 threadstack(void)
212 {
213 	Proc *p;
214 	Thread *t;
215 
216 	p = _threadgetproc();
217 	t = p->thread;
218 	return (ulong)&p - (ulong)t->stk;
219 }
220 
221 void
222 _threadready(Thread *t)
223 {
224 	Tqueue *q;
225 
226 	if(t == t->proc->idle){
227 		_threaddebug(DBGSCHED, "idle thread is ready");
228 		return;
229 	}
230 
231 	assert(t->state == Ready);
232 	_threaddebug(DBGSCHED, "readying %d.%d", t->proc->pid, t->id);
233 	q = &t->proc->ready;
234 	lock(&t->proc->readylock);
235 	t->next = nil;
236 	if(q->head==nil)
237 		q->head = t;
238 	else
239 		q->tail->next = t;
240 	q->tail = t;
241 	if(q->asleep){
242 		assert(q->asleep == 1);
243 		q->asleep = 0;
244 		/* lock passes to runthread */
245 		_threaddebug(DBGSCHED, "waking process %d", t->proc->pid);
246 		while(rendezvous((ulong)q, 0) == ~0){
247 			if(_threadexitsallstatus)
248 				exits(_threadexitsallstatus);
249 		}
250 	}else
251 		unlock(&t->proc->readylock);
252 }
253 
254 void
255 _threadidle(void)
256 {
257 	Tqueue *q;
258 	Thread *t, *idle;
259 	Proc *p;
260 
261 	p = _threadgetproc();
262 	q = &p->ready;
263 	lock(&p->readylock);
264 	assert(q->tail);
265 	idle = q->tail;
266 	if(q->head == idle){
267 		q->head = nil;
268 		q->tail = nil;
269 	}else{
270 		for(t=q->head; t->next!=q->tail; t=t->next)
271 			;
272 		t->next = nil;
273 		q->tail = t;
274 	}
275 	p->idle = idle;
276 	_threaddebug(DBGSCHED, "p->idle is %d\n", idle->id);
277 	unlock(&p->readylock);
278 }
279 
280 void
281 yield(void)
282 {
283 	_sched();
284 }
285 
286 void
287 threadstatus(void)
288 {
289 	Proc *p;
290 	Thread *t;
291 
292 	p = _threadgetproc();
293 	for(t=p->threads.head; t; t=t->nextt)
294 		fprint(2, "[%3d] %s userpc=%lux\n",
295 			t->id, psstate(t->state), t->userpc);
296 }
297