From: Ben Pfaff <blp@nicira.com>
Date: Wed, 21 Jan 2009 00:06:59 +0000 (-0800)
Subject: process: Avoid stealing pclose()'s exit status.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5ef2779ae46aa6c752792e3315d70cc65b14628b;p=openvswitch

process: Avoid stealing pclose()'s exit status.

When we use popen() and pclose(), pclose() wants to return the process's
exit status, but it can't if the SIGCHLD handler gets it first.  So,
instead of asking for any child process exit status in sigchld_handler(),
only ask for the exit status of registered PIDs.
---

diff --git a/lib/process.c b/lib/process.c
index d787b7bf..087ca6b8 100644
--- a/lib/process.c
+++ b/lib/process.c
@@ -337,21 +337,22 @@ process_wait(struct process *p)
 static void
 sigchld_handler(int signr UNUSED)
 {
-    for (;;) {
-        struct process *p;
-        int status;
-        pid_t pid;
-
-        pid = waitpid(-1, &status, WNOHANG);
-        if (pid <= 0) {
-            break;
-        }
+    struct process *p;
 
-        LIST_FOR_EACH (p, struct process, node, &all_processes) {
-            if (p->pid == pid) {
+    LIST_FOR_EACH (p, struct process, node, &all_processes) {
+        if (!p->exited) {
+            int retval, status;
+            do {
+                retval = waitpid(p->pid, &status, WNOHANG);
+            } while (retval == -1 && errno == EINTR);
+            if (retval == p->pid) {
                 p->exited = true;
                 p->status = status;
-                break;
+            } else if (retval < 0) {
+                /* XXX We want to log something but we're in a signal
+                 * handler. */
+                p->exited = true;
+                p->status = -1;
             }
         }
     }