provide event_reinit() to reinitialized an event_base after fork - necessary for epoll/kqueue

svn:r539

ChangeLog

@@ -5,6 +5,7 @@ Changes in current version:
  o bufferevent_write now uses a const source argument; report from Charles Kerr
  o improve documentation on event_base_loopexit; patch from Scott Lamb
  o New function, event_{base_}loopbreak.  Like event_loopexit, it makes an event loop stop executing and return.  Unlike event_loopexit, it keeps subsequent pending events from getting executed.  Patch from Scott Lamb
+ o provide event_reinit() to reintialize an event_base after fork
 
 Changes in 1.4.0:
  o allow \r or \n individually to separate HTTP headers instead of the standard "\r\n"; from Charles Kerr.

epoll.c

@@ -83,7 +83,8 @@ struct eventop epollops = {
 	epoll_del,
 	epoll_recalc,
 	epoll_dispatch,
-	epoll_dealloc
+	epoll_dealloc,
+	1 /* need reinit */
 };
 
 #ifdef HAVE_SETFD

event-internal.h

@@ -35,6 +35,18 @@ extern "C" {
 #include "min_heap.h"
 #include "evsignal.h"
 
+struct eventop {
+	const char *name;
+	void *(*init)(struct event_base *);
+	int (*add)(void *, struct event *);
+	int (*del)(void *, struct event *);
+	int (*recalc)(struct event_base *, void *, int);
+	int (*dispatch)(struct event_base *, void *, struct timeval *);
+	void (*dealloc)(struct event_base *, void *);
+	/* set if we need to reinitialize the event base */
+	int need_reinit;
+};
+
 struct event_base {
 	const struct eventop *evsel;
 	void *evbase;

event.c

@@ -250,6 +250,31 @@ event_base_free(struct event_base *base)
 	free(base);
 }
 
+/* reinitialized the event base after a fork */
+int
+event_reinit(struct event_base *base)
+{
+	const struct eventop *evsel = base->evsel;
+	int res = 0;
+	struct event *ev;
+
+	/* check if this event mechanism requires reinit */
+	if (!evsel->need_reinit)
+		return (0);
+
+	base->evbase = evsel->init(base);
+	if (base->evbase == NULL)
+		event_errx(1, "%s: could not reinitialize event mechanism",
+		    __func__);
+
+	TAILQ_FOREACH(ev, &base->eventqueue, ev_next) {
+		if (evsel->add(base, ev) == -1)
+			res = -1;
+	}
+
+	return (res);
+}
+
 int
 event_priority_init(int npriorities)
 {

event.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2004 Niels Provos <provos@citi.umich.edu>
+ * Copyright (c) 2000-2007 Niels Provos <provos@citi.umich.edu>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -257,16 +257,6 @@ TAILQ_HEAD (event_list, event);
 TAILQ_HEAD (evkeyvalq, evkeyval);
 #endif /* _EVENT_DEFINED_TQENTRY */
 
-struct eventop {
-	const char *name;
-	void *(*init)(struct event_base *);
-	int (*add)(void *, struct event *);
-	int (*del)(void *, struct event *);
-	int (*recalc)(struct event_base *, void *, int);
-	int (*dispatch)(struct event_base *, void *, struct timeval *);
-	void (*dealloc)(struct event_base *, void *);
-};
-
 /**
   Initialize the event API.
 
@@ -289,6 +279,17 @@ struct event_base *event_base_new(void);
  */
 struct event_base *event_init(void);
 
+/**
+  Reinitialized the event base after a fork
+
+  Some event mechanisms do not survive across fork.   The event base needs
+  to be reinitialized with the event_reinit() function.
+
+  @param base the event base that needs to be re-initialized
+  @return 0 if successful, or -1 if some events could not be re-added.
+  @see event_base_new(), event_init()
+*/
+int event_reinit(struct event_base *base);
 
 /**
   Loop to process events.

kqueue.c

@@ -58,6 +58,7 @@
 #endif
 
 #include "event.h"
+#include "event-internal.h"
 #include "log.h"
 
 #define EVLIST_X_KQINKERNEL	0x1000
@@ -87,7 +88,8 @@ const struct eventop kqops = {
 	kq_del,
 	kq_recalc,
 	kq_dispatch,
-	kq_dealloc
+	kq_dealloc,
+	1 /* need reinit */
 };
 
 void *

test/regress.c

@@ -42,6 +42,7 @@
 #include <sys/queue.h>
 #ifndef WIN32
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include <sys/signal.h>
 #include <unistd.h>
 #include <netdb.h>
@@ -446,6 +447,47 @@ test_simpletimeout(void)
 }
 
 #ifndef WIN32
+void
+test_fork(void)
+{
+	int status;
+	struct event ev;
+	pid_t pid;
+
+	setup_test("After fork: ");
+
+	write(pair[0], TEST1, strlen(TEST1)+1);
+	shutdown(pair[0], SHUT_WR);
+
+	event_set(&ev, pair[1], EV_READ, simple_read_cb, &ev);
+	if (event_add(&ev, NULL) == -1)
+		exit(1);
+
+	if ((pid = fork()) == 0) {
+		/* in the child */
+		extern struct event_base *current_base;
+		if (event_reinit(current_base) == -1) {
+			fprintf(stderr, "FAILED (reinit)\n");
+			exit(1);
+		}
+
+		event_dispatch();
+
+		exit(test_ok == 0);
+	}
+
+	event_del(&ev);
+
+	if (waitpid(pid, &status, 0) == -1) {
+		fprintf(stderr, "FAILED (fork)\n");
+		exit(1);
+	}
+	
+	test_ok = WEXITSTATUS(status) == 0;
+
+	cleanup_test();
+}
+
 void
 test_simplesignal(void)
 {
@@ -1227,6 +1269,10 @@ main (int argc, char **argv)
 
 	dns_suite();
 	
+#ifndef WIN32
+	test_fork();
+#endif
+
 	test_simpleread();
 
 	test_simplewrite();