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module/script: no need to handle SIGCHLD

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Assume that a closed pipe means the child died. Even if it hasn’t, we
can’t read anymore from it. We’ll end up killing it anyway before
returning from run().
This commit is contained in:
Daniel Eklöf 2020-11-02 19:14:15 +01:00
parent e0169d38f3
commit ba54e709ee
No known key found for this signature in database
GPG key ID: 5BBD4992C116573F
1 changed files with 14 additions and 49 deletions
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63
modules/script.c
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@ -10,7 +10,6 @@
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/signalfd.h>
#define LOG_MODULE "script"
#define LOG_ENABLE_DBG 0
@ -315,34 +314,13 @@ data_received(struct module *mod, const char *data, size_t len)
}
static int
run_loop(struct module *mod, int comm_fd)
run_loop(struct module *mod, pid_t pid, int comm_fd)
{
//struct private *m = mod;
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SIGCHLD);
/* Block normal signal handling - we're using a signalfd instead */
sigset_t original_mask;
if (pthread_sigmask(SIG_BLOCK, &mask, &original_mask) < 0) {
LOG_ERRNO("failed to block SIGCHLD");
return -1;
}
int sig_fd = signalfd(-1, &mask, SFD_NONBLOCK | SFD_CLOEXEC);
if (sig_fd < 0) {
LOG_ERRNO("failed to create signal FD");
pthread_sigmask(SIG_SETMASK, &original_mask, NULL);
return -1;
}
int ret = 0;
while (true) {
struct pollfd fds[] = {
{.fd = mod->abort_fd, .events = POLLIN},
{.fd = sig_fd, .events = POLLIN},
{.fd = comm_fd, .events = POLLIN},
};
@ -354,7 +332,7 @@ run_loop(struct module *mod, int comm_fd)
break;
}
if (fds[2].revents & POLLIN) {
if (fds[1].revents & POLLIN) {
char data[4096];
ssize_t amount = read(comm_fd, data, sizeof(data));
if (amount < 0) {
@ -373,36 +351,17 @@ run_loop(struct module *mod, int comm_fd)
}
if (fds[1].revents & POLLHUP) {
LOG_ERR("signal FD closed unexpectedly");
ret = 1;
break;
}
if (fds[2].revents & POLLHUP) {
/* Child's stdout closed */
LOG_DBG("script pipe closed (script terminated?)");
break;
}
if (fds[0].revents & POLLIN)
break;
if (fds[1].revents & POLLIN) {
struct signalfd_siginfo info;
ssize_t amount = read(sig_fd, &info, sizeof(info));
if (amount < 0) {
LOG_ERRNO("failed to read from signal FD");
break;
}
assert(info.ssi_signo == SIGCHLD);
LOG_WARN("script died");
if (fds[0].revents & POLLIN) {
/* Aborted */
break;
}
}
close(sig_fd);
pthread_sigmask(SIG_SETMASK, &original_mask, NULL);
return ret;
}
@ -411,12 +370,14 @@ run(struct module *mod)
{
struct private *m = mod->private;
/* Pipe to detect exec() failures */
int exec_pipe[2];
if (pipe2(exec_pipe, O_CLOEXEC) < 0) {
LOG_ERRNO("failed to create pipe");
return -1;
}
/* Stdout redirection pipe */
int comm_pipe[2];
if (pipe(comm_pipe) < 0) {
LOG_ERRNO("failed to create stdin/stdout redirection pipe");
@ -438,13 +399,14 @@ run(struct module *mod)
if (pid == 0) {
/* Child */
/* Construct argv for execvp() */
char *argv[1 + m->argc + 1];
argv[0] = m->path;
for (size_t i = 0; i < m->argc; i++)
argv[i + 1] = m->argv[i];
argv[1 + m->argc] = NULL;
/* Restore signal handlers */
/* Restore signal handlers and signal mask */
sigset_t mask;
sigemptyset(&mask);
@ -457,6 +419,7 @@ run(struct module *mod)
goto fail;
}
/* New process group, so that we can use killpg() */
setpgid(0, 0);
/* Close pipe read ends */
@ -505,6 +468,7 @@ run(struct module *mod)
int _errno;
static_assert(sizeof(_errno) == sizeof(errno), "errno size mismatch");
/* Wait for errno from child, or FD being closed in execvp() */
int r = read(exec_pipe[0], &_errno, sizeof(_errno));
close(exec_pipe[0]);
@ -521,10 +485,11 @@ run(struct module *mod)
return -1;
}
/* Pipe was closed. I.e. execvp() succeeded */
assert(r == 0);
LOG_DBG("script running under PID=%u", pid);
int ret = run_loop(mod, comm_pipe[0]);
int ret = run_loop(mod, pid, comm_pipe[0]);
close(comm_pipe[0]);
if (waitpid(pid, NULL, WNOHANG) == 0) {
killpg(pid, SIGTERM);