libposix: initial changes to POSIX_kill

sys/src/lib/posix/initlib.c

@@ -22,7 +22,7 @@
 
 extern int *__libposix_errors_codes;
 extern WaitList **__libposix_wait_list;
-extern Child **__libposix_child_list;
+extern ChildList **__libposix_child_list;
 static int __initialized;
 
 static void
@@ -44,7 +44,7 @@ libposix_init(int argc, char *argv[], PosixInit init)
 	extern int *__libposix_sigchld_target_pid;
 
 	WaitList *wait_list;
-	Child *child_list;
+	ChildList *child_list;
 	int status;
 	int error_codes[ERRNO_LAST-ERRNO_FIRST];
 	unsigned char signals_to_code[256];
@@ -64,7 +64,7 @@ libposix_init(int argc, char *argv[], PosixInit init)
 
 	/* initialize child_list; used when SIGCHLD is enabled */
 	child_list = nil;
-	__libposix_wait_list = &child_list;
+	__libposix_child_list = &child_list;
 
 	/* initialize signal handling */
 	memset(signals_to_code, 0, sizeof(signals_to_code));

sys/src/lib/posix/internal.h

@@ -23,11 +23,11 @@ struct WaitList
 	WaitList *next;
 };
 
-typedef struct Child Child;
-struct Child
+typedef struct ChildList ChildList;
+struct ChildList
 {
 	int pid;
-	Child *next;
+	ChildList *next;
 };
 
 extern void __libposix_files_check_conf(void);
@@ -48,3 +48,4 @@ extern void __libposix_free_wait_list(void);
 
 extern void __libposix_setup_new_process(void);
 
+extern int __libposix_note_to_signal(char *note);

sys/src/lib/posix/processes.c

@@ -23,7 +23,7 @@
 extern char **environ;
 
 WaitList **__libposix_wait_list;
-Child **__libposix_child_list;
+ChildList **__libposix_child_list;
 
 static PosixExitStatusTranslator __libposix_exit_status_translator;
 static int __libposix_wnohang;
@@ -34,7 +34,6 @@ static int
 fork_without_sigchld(int *errnop)
 {
 	int pid = fork();
-
 	if(pid == 0)
 		__libposix_setup_new_process();
 	return pid;
@@ -42,14 +41,6 @@ fork_without_sigchld(int *errnop)
 
 int (*__libposix_fork)(int *errnop) = fork_without_sigchld;
 
-void
-__libposix_setup_new_process(void)
-{
-	/* reset wait list for the child */
-	*__libposix_wait_list = nil;
-	*__libposix_child_list = nil;
-}
-
 void
 __libposix_free_wait_list(void)
 {
@@ -69,6 +60,33 @@ __libposix_free_wait_list(void)
 	}
 }
 
+void
+__libposix_free_child_list(void)
+{
+	ChildList *l, *c;
+
+	/* free the wait list as the memory is shared */
+	l = *__libposix_child_list;
+	if(l != nil){
+		*__libposix_child_list = nil;
+		do
+		{
+			c = l;
+			l = c->next;
+			free(c);
+		}
+		while (l != nil);
+	}
+}
+
+void
+__libposix_setup_new_process(void)
+{
+	/* reset wait list for the child */
+	__libposix_free_wait_list();
+	__libposix_free_child_list();
+}
+
 void
 POSIX_exit(int code)
 {

sys/src/lib/posix/sigchlds.c

@@ -24,7 +24,7 @@
 /* rendezvous points */
 extern unsigned char *__signals_to_code_map;
 extern unsigned char *__code_to_signal_map;
-extern Child **__libposix_child_list;
+extern ChildList **__libposix_child_list;
 
 /* pointer to the pid to forward notes to */
 int *__libposix_sigchld_target_pid;
@@ -44,8 +44,24 @@ release_inherited_resources(void)
 static void
 forwarding_note_handler(void *ureg, char *note)
 {
-	postnote(PNPROC, *__libposix_sigchld_target_pid, note);
-	noted(NCONT);
+	int sig;
+	PosixSignals psig;
+	if(strncmp(note, __POSIX_SIGNAL_PREFIX, __POSIX_SIGNAL_PREFIX_LEN) == 0){
+		sig = __libposix_note_to_signal(note);
+		if(sig < __min_known_sig || sig > __max_known_sig){
+			/* Ignore unknown signals */
+			noted(NCONT);
+		}
+		psig = __code_to_signal_map[sig];
+		switch(psig){
+			
+		}
+		postnote(PNPROC, *__libposix_sigchld_target_pid, note);
+		noted(NCONT);
+	} else {
+		/* what happened? */
+		noted(NDFLT);
+	}
 }
 
 static void
@@ -93,6 +109,7 @@ fork_with_sigchld(int *errnop)
 	int p2c;
 	long c2p = -1, child = -1;
 	char proxy_name[256];
+	ChildList *c;
 
 	/* Father here:
 	 * - create P2C
@@ -173,9 +190,11 @@ fork_with_sigchld(int *errnop)
 		break;
 	}
 
-	/* TODO: register p2c among known children so that kill can
-	 * handle them properly.
-	 */
+	/* no need to lock: the child list is private */
+	c = malloc(sizeof(ChildList));
+	c->pid = p2c;
+	c->next = *__libposix_child_list;
+	*__libposix_child_list = c;
 
 	return p2c;
 }

sys/src/lib/posix/signals.c

@@ -69,7 +69,7 @@
  * Calling libposix_emulate_SIGCHLD() during libposix initialization
  * will enable this machinery for the whole life of the process.
  *
- * Such emulation change the way fork and kill works.
+ * Such emulation changes the way POSIX_fork and POSIX_kill works.
  *
  * Each fork() will spawn two additional processes that are designed
  * to proxy signals between the parent and the desired child:
@@ -162,7 +162,7 @@ terminated_by_signal(int sig)
 }
 
 int
-send_control_msg(int pid, char *msg)
+__libposix_send_control_msg(int pid, char *msg)
 {
 	int fd, n;
 	char buf[256];
@@ -187,14 +187,13 @@ ErrorBeforeOpen:
 	return 0;
 }
 
-/* Executes a PosixSignalDisposition for pid.
- *
- * MUST be called by POSIX_kill for unblockable signals.
+/* Executes a PosixSignalDisposition.
  */
 static int
-execute_disposition(int sig, PosixSignalDisposition action, int pid)
+execute_disposition(int sig, PosixSignalDisposition action)
 {
 	switch(action){
+	case ResumeTheProcess:	// the sender resumed us already
 	case SignalHandled:
 		return 1;
 	case TerminateTheProcess:
@@ -202,17 +201,46 @@ execute_disposition(int sig, PosixSignalDisposition action, int pid)
 		terminated_by_signal(sig);
 		break;
 	case StopTheProcess:
-		if(pid < 0)
-			sysfatal("libposix: signal %d with stop disposition reached process %d", sig, pid);
-		return send_control_msg(pid, "stop");
-	case ResumeTheProcess:
-		if(pid < 0)
-			sysfatal("libposix: signal %d with continue disposition reached process %d", sig, pid);
-		return send_control_msg(pid, "start");
+		return __libposix_send_control_msg(getpid(), "stop");
 	}
 	return 0;
 }
 
+PosixError
+__libposix_receive_signal(int sig)
+{
+	if(__libposix_signal_trampoline(sig))
+		action = SignalHandled;
+	else
+		action = default_signal_disposition(sig);
+	if(!execute_disposition(sig, action))
+		return PosixEPERM;
+	return 0;
+}
+
+PosixError
+__libposix_notify_signal_to_process(int pid, int signal)
+{
+	char buf[128];
+	int fd, n;
+
+	snprint(buf, sizeof(buf), "/proc/%d/note", pid);
+	if(access(file, AWRITE) != 0){
+		if(access(file, AEXIST) == 0)
+			return PosixEPERM;
+		else
+			return PosixESRCH;
+	}
+
+	fd = open(buf, OWRITE);
+	if(fd < 0)
+		return PosixEPERM;
+	n = snprint(buf, sizeof(buf), __POSIX_SIGNAL_PREFIX "%d", signal);
+	write(fd, buf, n);
+	close(fd);
+	return 0;
+}
+
 static int
 send_signal(int *errnop, int pid, int signal)
 {
@@ -324,21 +352,21 @@ POSIX_kill(int *errnop, int pid, int sig)
 	switch(signal){
 	case PosixSIGKILL:
 		if(pid > 0)
-		if(!send_control_msg(pid, "kill")){
+		if(!__libposix_send_control_msg(pid, "kill")){
 			*errnop = __libposix_get_errno(PosixEPERM);
 			return -1;
 		}
 		break;
 	case PosixSIGSTOP:
 		if(pid > 0)
-		if(!send_control_msg(pid, "stop")){
+		if(!__libposix_send_control_msg(pid, "stop")){
 			*errnop = __libposix_get_errno(PosixEPERM);
 			return -1;
 		}
 		break;
 	case PosixSIGCONT:
 		if(pid > 0)
-		if(!send_control_msg(pid, "start")){
+		if(!__libposix_send_control_msg(pid, "start")){
 			*errnop = __libposix_get_errno(PosixEPERM);
 			return -1;
 		}
@@ -356,6 +384,11 @@ translate_jehanne_note(char *note)
 	return 0;
 }
 
+int
+__libposix_note_to_signal(char *note)
+{
+	return atoi(note+__POSIX_SIGNAL_PREFIX_LEN);
+}
 
 int
 __libposix_note_handler(void *ureg, char *note)
@@ -364,7 +397,7 @@ __libposix_note_handler(void *ureg, char *note)
 	PosixSignalDisposition action;
 	if(strncmp(note, __POSIX_SIGNAL_PREFIX, __POSIX_SIGNAL_PREFIX_LEN) != 0)
 		return translate_jehanne_note(note); // TODO: should we translate common notes?
-	sig = atoi(note+__POSIX_SIGNAL_PREFIX_LEN);
+	sig = __libposix_note_to_signal(note);
 	if(sig < __min_known_sig || sig > __max_known_sig)
 		sysfatal("libposix: '%s' does not carry a signal", note);
 	*__handling_external_signal = 1;