[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] [PATCH v3] network scripts: don't block SIGCHLD before fork

From: Michael Roth
Subject: [Qemu-devel] [PATCH v3] network scripts: don't block SIGCHLD before forking
Date: Wed, 7 Dec 2011 21:48:07 -0600

This patch fixes a bug where child processes of launch_script() can
misbehave due to SIGCHLD being blocked. In the case of `sudo`, this
causes a permanent hang.

Previously a SIGCHLD handler was added to reap fork_exec()'d zombie
processes by calling waitpid(-1, ...). This required other
fork()/waitpid() callers to temporarilly block SIGCHILD to avoid
having the final wait status being intercepted by the SIGCHLD


Since then, the qemu_add_child_watch() interface was added to allow
registration of such processes and reap only from that specific set
of PIDs:


As a result, we can now avoid blocking SIGCHLD in launch_script(), so
drop that behavior.

Signed-off-by: Michael Roth <address@hidden>
 net/tap.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/net/tap.c b/net/tap.c
index 1f26dc9..6c27a94 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -346,15 +346,10 @@ static TAPState *net_tap_fd_init(VLANState *vlan,
 static int launch_script(const char *setup_script, const char *ifname, int fd)
-    sigset_t oldmask, mask;
     int pid, status;
     char *args[3];
     char **parg;
-    sigemptyset(&mask);
-    sigaddset(&mask, SIGCHLD);
-    sigprocmask(SIG_BLOCK, &mask, &oldmask);
     /* try to launch network script */
     pid = fork();
     if (pid == 0) {
@@ -378,7 +373,6 @@ static int launch_script(const char *setup_script, const 
char *ifname, int fd)
         while (waitpid(pid, &status, 0) != pid) {
             /* loop */
-        sigprocmask(SIG_SETMASK, &oldmask, NULL);
         if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
             return 0;

reply via email to

[Prev in Thread] Current Thread [Next in Thread]