[Lprng-devel] [PATCH] Forget pid of child that have exited.

[Ales N. <al...@su...>]

We need to forget about the child that had exited and had already
been successfully waited for. Otherwise the LPRng will try to kill
that pid on its exit - but the pid may be assigned to completely
another process.

The patch is adding the function forget_child(pid_t), which walks
through the list of childs and tries to find the specified one
and remove it. The function is called after successfull waitpid()
call.

Signed-off-by: Ales Novak <al...@su...>
---
 src/common/child.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/src/common/child.c b/src/common/child.c
index 8c4ee3d..5476c75 100644
--- a/src/common/child.c
+++ b/src/common/child.c
@@ -34,6 +34,36 @@
 #  include <sys/ttold.h>
 #endif
 
+/*
+ * When the child was successfully waited on, it stayed in the
+ * Process_list and henceforth the lpd tried to kill it when
+ * cleaning up. But the pid may have been assigned to another
+ * process!
+ *
+ * So what is neccessary is to walk through the process list,
+ * and remove the pid which has just exited (or have successfully
+ * been waited for, to be precise).
+ *
+ * The removal is done by replacing the record by the last one in
+ * the list and decrementing the record count.
+ */
+static void forget_child(pid_t pid)
+{
+	int i;
+
+	for( i = 0; i < Process_list.count; ++i ){
+		if (pid == Cast_ptr_to_int(Process_list.list[i]))
+			break;
+	}
+
+	if (i < Process_list.count) {
+		DEBUG2("forget_child: found the child with pid %d", pid);
+		Process_list.list[i] = Process_list.list[Process_list.count-1];
+		Process_list.count --;
+	} else {
+		DEBUG2("forget_child: child with pid %d not found", pid);
+	}
+}
 
 /*
  * Patrick Powell
@@ -51,6 +81,7 @@ pid_t plp_waitpid (pid_t pid, plp_status_t *statusPtr, int options)
 	report = waitpid(pid, statusPtr, options );
 	DEBUG2("plp_waitpid: returned %d, status %s", report,
 		Decode_status( statusPtr ) );
+	if (report > 0) forget_child(pid);
 	return report;
 }
 
-- 
1.8.1.4