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network scripts: don't block SIGCHLD before forking 

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
handler:

7c3370d4fe

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:

4d54ec7898

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

Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Michael Roth 2011-12-07 21:48:07 -06:00 committed by Anthony Liguori
parent f603a687ff
commit 885660bd48
1 changed files with 0 additions and 6 deletions
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6
net/tap.c
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@ -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;