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-rw-r--r--Changes1
-rw-r--r--ev.c10
-rw-r--r--ev.pod56
3 files changed, 61 insertions, 6 deletions
diff --git a/Changes b/Changes
index e5d53d1..6f1e9e0 100644
--- a/Changes
+++ b/Changes
@@ -4,6 +4,7 @@ Revision history for libev, a high-performance and full-featured event loop
- implement ev_async watchers.
- only initialise signal pipe on demand.
- make use of sig_atomic_t configurable.
+ - improved ev_child documentation.
3.0 Mon Jan 28 13:14:47 CET 2008
- API/ABI bump to version 3.0.
diff --git a/ev.c b/ev.c
index 34e3fd9..4e8deda 100644
--- a/ev.c
+++ b/ev.c
@@ -914,7 +914,7 @@ static ev_signal childev;
#endif
void inline_speed
-child_reap (EV_P_ ev_signal *sw, int chain, int pid, int status)
+child_reap (EV_P_ int chain, int pid, int status)
{
ev_child *w;
int traced = WIFSTOPPED (status) || WIFCONTINUED (status);
@@ -924,7 +924,7 @@ child_reap (EV_P_ ev_signal *sw, int chain, int pid, int status)
if ((w->pid == pid || !w->pid)
&& (!traced || (w->flags & 1)))
{
- ev_set_priority (w, ev_priority (sw)); /* need to do it *now* */
+ ev_set_priority (w, EV_MAXPRI); /* need to do it *now*, this *must* be the same prio as the signal watcher itself */
w->rpid = pid;
w->rstatus = status;
ev_feed_event (EV_A_ (W)w, EV_CHILD);
@@ -948,13 +948,13 @@ childcb (EV_P_ ev_signal *sw, int revents)
|| 0 >= (pid = waitpid (-1, &status, WNOHANG | WUNTRACED)))
return;
- /* make sure we are called again until all childs have been reaped */
+ /* make sure we are called again until all children have been reaped */
/* we need to do it this way so that the callback gets called before we continue */
ev_feed_event (EV_A_ (W)sw, EV_SIGNAL);
- child_reap (EV_A_ sw, pid, pid, status);
+ child_reap (EV_A_ pid, pid, status);
if (EV_PID_HASHSIZE > 1)
- child_reap (EV_A_ sw, 0, pid, status); /* this might trigger a watcher twice, but feed_event catches that */
+ child_reap (EV_A_ 0, pid, status); /* this might trigger a watcher twice, but feed_event catches that */
}
#endif
diff --git a/ev.pod b/ev.pod
index 812978b..b41cc3d 100644
--- a/ev.pod
+++ b/ev.pod
@@ -1456,7 +1456,32 @@ Example: Try to exit cleanly on SIGINT and SIGTERM.
=head2 C<ev_child> - watch out for process status changes
Child watchers trigger when your process receives a SIGCHLD in response to
-some child status changes (most typically when a child of yours dies).
+some child status changes (most typically when a child of yours dies). It
+is permissible to install a child watcher I<after> the child has been
+forked (which implies it might have already exited), as long as the event
+loop isn't entered (or is continued from a watcher).
+
+Only the default event loop is capable of handling signals, and therefore
+you can only rgeister child watchers in the default event loop.
+
+=head3 Process Interaction
+
+Libev grabs C<SIGCHLD> as soon as the default event loop is
+initialised. This is necessary to guarantee proper behaviour even if
+the first child watcher is started after the child exits. The occurance
+of C<SIGCHLD> is recorded asynchronously, but child reaping is done
+synchronously as part of the event loop processing. Libev always reaps all
+children, even ones not watched.
+
+=head3 Overriding the Built-In Processing
+
+Libev offers no special support for overriding the built-in child
+processing, but if your application collides with libev's default child
+handler, you can override it easily by installing your own handler for
+C<SIGCHLD> after initialising the default loop, and making sure the
+default loop never gets destroyed. You are encouraged, however, to use an
+event-based approach to child reaping and thus use libev's support for
+that, so other libev users can use C<ev_child> watchers freely.
=head3 Watcher-Specific Functions and Data Members
@@ -1490,6 +1515,35 @@ C<waitpid> and C<sys/wait.h> documentation for details).
=back
+=head3 Examples
+
+Example: C<fork()> a new process and install a child handler to wait for
+its completion.
+
+ ev_child cw;
+
+ static void
+ child_cb (EV_P_ struct ev_child *w, int revents)
+ {
+ ev_child_stop (EV_A_ w);
+ printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
+ }
+
+ pid_t pid = fork ();
+
+ if (pid < 0)
+ // error
+ else if (pid == 0)
+ {
+ // the forked child executes here
+ exit (1);
+ }
+ else
+ {
+ ev_child_init (&cw, child_cb, pid, 0);
+ ev_child_start (EV_DEFAULT_ &cw);
+ }
+
=head2 C<ev_stat> - did the file attributes just change?