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	tbetter exec handling - plan9port - [fork] Plan 9 from user space
	git clone git://src.adamsgaard.dk/plan9port
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	---
	commit 8cbd854a8ab2c4f8c738c5bea5263217cb892a77
	parent 03417610742c4a67bb0345a8fa0fb4e13dee07f7
	Author: rsc <devnull@localhost>
	Date: Mon, 27 Dec 2004 19:11:33 +0000

	better exec handling

	Diffstat:
	M src/libthread/Linux.c \| 33 +++--------------------------…
	M src/libthread/exec.c \| 62 +++++++++++++----------------…
	M src/libthread/pthread.c \| 6 ------
	M src/libthread/thread.c \| 19 ++++++++++++++-----
	M src/libthread/threadimpl.h \| 1 +

	5 files changed, 43 insertions(+), 78 deletions(-)
	---
	diff --git a/src/libthread/Linux.c b/src/libthread/Linux.c
	t@@ -99,13 +99,15 @@ again:
	sigdelset(&mask, SIGUSR1);
	sigsuspend(&mask);

	+//print("%d %d awake again\n", time(0), getpid());
	+
	/*
	* We're awake. Make USR1 not interrupt system calls.
	*/
	lock(r->l);
	ignusr1(1);
	if(r->asleep && r->pid == getpid()){
	-print("resleep %d\n", getpid());
	+//print("resleep %d\n", getpid());
	/* Didn't really wake up - signal from something else */
	goto again;
	}
	t@@ -266,35 +268,6 @@ threadexitsall(char *msg)
	}

	/*
	- * exec - need to arrange for wait proc to run
	- * the execs so it gets the wait messages
	- */
	-int
	-_runthreadspawn(int fd, char cmd, char **argv)
	-{
	- Execjob e;
	- int pid;
	-
	- e.fd = fd;
	- e.cmd = cmd;
	- e.argv = argv;
	- e.c = chancreate(sizeof(ulong), 0);
	-print("%d run\n", time(0));
	- qlock(&_threadexeclock);
	- sendp(_threadexecchan, &e);
	-print("%d sent\n", time(0));
	- while(_threadexecproc == nil)
	- yield();
	- kill(_threadexecproc->osprocid, SIGUSR2);
	-print("%d killed\n", time(0));
	- pid = recvul(e.c);
	- qunlock(&_threadexeclock);
	-print("%d ran\n", time(0));
	- return pid;
	-}
	-
	-
	-/*
	* per-process data, indexed by pid
	*
	* could use modify_ldt and a segment register
	diff --git a/src/libthread/exec.c b/src/libthread/exec.c
	t@@ -6,41 +6,42 @@

	static Lock thewaitlock;
	static Channel *thewaitchan;
	-Channel *_dowaitchan;
	-Channel *_threadexecchan;
	-Proc *_threadexecproc;
	-QLock _threadexeclock;

	static void
	-execthread(void *v)
	-{
	- Execjob *e;
	-
	- USED(v);
	- while((e = recvp(_threadexecchan)) != nil){
	-print("%d doexec pid %d\n", time(0), getpid());
	- sendul(e->c, _threadspawn(e->fd, e->cmd, e->argv));
	- }
	-}
	-
	-static void
	-waitproc(void *v)
	+execproc(void *v)
	{
	+ int pid;
	Channel *c;
	+ Execjob *e;
	Waitmsg *w;

	- _threadsetsysproc();
	- _threadexecproc = proc();
	- threadcreate(execthread, nil, 65536);
	- for(;;){
	- while((w = wait()) == nil)
	- if(errno == ECHILD)
	- recvul(_dowaitchan);
	+ e = v;
	+ pid = _threadspawn(e->fd, e->cmd, e->argv);
	+ sendul(e->c, pid);
	+ if(pid > 0){
	+ w = waitfor(pid);
	if((c = thewaitchan) != nil)
	sendp(c, w);
	else
	free(w);
	}
	+ threadexits(nil);
	+}
	+
	+int
	+_runthreadspawn(int fd, char cmd, char **argv)
	+{
	+ int pid;
	+ Execjob e;
	+
	+ e.fd = fd;
	+ e.cmd = cmd;
	+ e.argv = argv;
	+ e.c = chancreate(sizeof(void*), 0);
	+ proccreate(execproc, &e, 65536);
	+ pid = recvul(e.c);
	+ chanfree(e.c);
	+ return pid;
	}

	Channel*
	t@@ -104,28 +105,15 @@ _threadspawn(int fd[3], char cmd, char argv[])
	close(fd[1]);
	if(fd[2] != fd[1] && fd[2] != fd[0])
	close(fd[2]);
	- channbsendul(_dowaitchan, 1);
	return pid;
	}

	int
	threadspawn(int fd[3], char cmd, char argv[])
	{
	- if(_dowaitchan == nil){
	- lock(&thewaitlock);
	- if(_dowaitchan == nil){
	- _dowaitchan = chancreate(sizeof(ulong), 1);
	- chansetname(_dowaitchan, "dowaitchan");
	- _threadexecchan = chancreate(sizeof(void*), 1);
	- chansetname(_threadexecchan, "execchan");
	- proccreate(waitproc, nil, STACK);
	- }
	- unlock(&thewaitlock);
	- }
	return _runthreadspawn(fd, cmd, argv);
	}

	-
	int
	_threadexec(Channel cpid, int fd[3], char cmd, char *argv[])
	{
	diff --git a/src/libthread/pthread.c b/src/libthread/pthread.c
	t@@ -130,9 +130,3 @@ _pthreadinit(void)
	pthread_key_create(&prockey, 0);
	}

	-int
	-_runthreadspawn(int fd, char cmd, char **argv)
	-{
	- return _threadspawn(fd, cmd, argv);
	-}
	-
	diff --git a/src/libthread/thread.c b/src/libthread/thread.c
	t@@ -138,15 +138,23 @@ _threadready(_Thread *t)
	p = t->proc;
	lock(&p->lock);
	addthread(&p->runqueue, t);
	- _procwakeup(&p->runrend);
	+//print("%d wake for job %d->%d\n", time(0), getpid(), p->osprocid);
	+ if(p != proc())
	+ _procwakeup(&p->runrend);
	unlock(&p->lock);
	}

	-void
	+int
	threadyield(void)
	{
	- _threadready(proc()->thread);
	+ int n;
	+ Proc *p;
	+
	+ p = proc();
	+ n = p->nswitch;
	+ _threadready(p->thread);
	_threadswitch();
	+ return p->nswitch - n;
	}

	void
	t@@ -184,13 +192,14 @@ scheduler(Proc *p)
	if(p->nthread == 0)
	goto Out;
	p->runrend.l = &p->lock;
	-print("sleep for jobs %d\n", getpid());
	+//print("%d sleep for jobs %d\n", time(0), getpid());
	_procsleep(&p->runrend);
	-print("wake from jobs %d\n", getpid());
	+//print("%d wake from jobs %d\n", time(0), getpid());
	}
	delthread(&p->runqueue, t);
	unlock(&p->lock);
	p->thread = t;
	+ p->nswitch++;
	// print("run %s %d\n", t->name, t->id);
	contextswitch(&p->schedcontext, &t->context);
	p->thread = nil;
	diff --git a/src/libthread/threadimpl.h b/src/libthread/threadimpl.h
	t@@ -74,6 +74,7 @@ struct Proc
	uint osprocid;
	#endif
	Lock lock;
	+ int nswitch;
	_Thread *thread;
	_Threadlist runqueue;
	_Threadlist allthreads;