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/*
* Set up a dedicated proc to handle calls to exec.
* The proc also waits for child messages.
* This way, each proc scheduler need not worry
* about calling wait in its main loop.
*
* To be included from other files (e.g., Linux-clone.c).
*/
typedef struct Xarg Xarg;
struct Xarg
{
Channel *pidc;
int fd[3];
char *prog;
char **args;
int freeargs;
Channel *ret;
int errn;
char errstr[ERRMAX];
};
static Proc *_threadexecproc;
static Channel *_threadexecchan;
static Lock threadexeclock;
/*
* Called to poll for any kids of this pthread.
* We have a separate proc responsible for exec,
* so this is a no-op.
*/
void
_threadwaitkids(Proc *p)
{
}
#define WAITSIG SIGCHLD
/*
* Separate process to wait for child messages.
* Also runs signal handlers and runs all execs.
*/
static void
nop(int sig)
{
USED(sig);
}
static void
_threadwaitproc(void *v)
{
Channel *c;
Waitmsg *w;
sigset_t mask;
int ret, nkids;
Xarg *xa;
nkids = 0;
sigemptyset(&mask);
siginterrupt(WAITSIG, 1);
signal(WAITSIG, nop);
sigaddset(&mask, WAITSIG);
sigprocmask(SIG_BLOCK, &mask, nil);
USED(v);
for(;;){
while((nkids > 0 ? nbrecv : recv)(_threadexecchan, &xa) == 1){
ret = _threadexec(xa->pidc, xa->fd, xa->prog, xa->args, xa->freeargs);
if(ret > 0)
nkids++;
else{
rerrstr(xa->errstr, sizeof xa->errstr);
xa->errn = errno;
}
sendul(xa->ret, ret);
}
if(nkids > 0){
sigprocmask(SIG_UNBLOCK, &mask, nil);
w = wait();
sigprocmask(SIG_BLOCK, &mask, nil);
if(w == nil && errno == ECHILD){
fprint(2, "wait returned ECHILD but nkids=%d; reset\n", nkids);
nkids = 0;
}
if(w){
nkids--;
if((c = _threadwaitchan) != nil)
sendp(c, w);
else
free(w);
}
}
}
}
static void _kickexecproc(void);
int
_callthreadexec(Channel *pidc, int fd[3], char *prog, char *args[], int freeargs)
{
int ret;
Xarg xa;
if(_threadexecchan == nil){
lock(&threadexeclock);
if(_threadexecchan == nil)
_threadfirstexec();
unlock(&threadexeclock);
}
xa.pidc = pidc;
xa.fd[0] = fd[0];
xa.fd[1] = fd[1];
xa.fd[2] = fd[2];
xa.prog = prog;
xa.args = args;
xa.freeargs = freeargs;
xa.ret = chancreate(sizeof(ulong), 1);
sendp(_threadexecchan, &xa);
_kickexecproc();
ret = recvul(xa.ret);
if(ret < 0){
werrstr("%s", xa.errstr);
errno = xa.errn;
}
chanfree(xa.ret);
return ret;
}
/*
* Called before the first exec.
*/
void
_threadfirstexec(void)
{
int id;
Proc *p;
_threadexecchan = chancreate(sizeof(Xarg*), 1);
id = proccreate(_threadwaitproc, nil, 32*1024);
/*
* Sleazy: decrement threadnprocs so that
* the existence of the _threadwaitproc proc
* doesn't keep us from exiting.
*/
lock(&_threadpq.lock);
--_threadnprocs;
for(p=_threadpq.head; p; p=p->next)
if(p->threads.head && p->threads.head->id == id)
break;
if(p == nil)
sysfatal("cannot find exec proc");
unlock(&_threadpq.lock);
_threadexecproc = p;
}
/*
* Called after the thread t has been rescheduled.
* Kick the exec proc in case it is in the middle of a wait.
*/
static void
_kickexecproc(void)
{
kill(_threadexecproc->pid, WAITSIG);
}
/*
* Called before exec.
*/
void
_threadbeforeexec(void)
{
}
/*
* Called after exec.
*/
void
_threadafterexec(void)
{
}
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