liblogwrap: use POLLHUP flag to check when a child dies
Replace the old signal handling mechanism with a check of POLLHUP
to check when the child has died.
See http://b/8333626
Change-Id: Ic9909b6660b1c3d1ed3015568b1a1ee1c25afe20
diff --git a/logwrapper/logwrap.c b/logwrapper/logwrap.c
index 129ffb1..bf91977 100644
--- a/logwrapper/logwrap.c
+++ b/logwrapper/logwrap.c
@@ -17,7 +17,6 @@
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
-#include <signal.h>
#include <poll.h>
#include <sys/wait.h>
#include <stdio.h>
@@ -35,7 +34,6 @@
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
-static int signal_fd_write;
static pthread_mutex_t fd_mutex = PTHREAD_MUTEX_INITIALIZER;
#define ERROR(fmt, args...) \
@@ -50,94 +48,77 @@
_exit(-1); \
} while(0)
-static int parent(const char *tag, int parent_read, int signal_fd, pid_t pid,
- int *chld_sts, bool logwrap) {
+static int parent(const char *tag, int parent_read, pid_t pid, int *chld_sts,
+ bool logwrap) {
int status = 0;
char buffer[4096];
struct pollfd poll_fds[] = {
[0] = {
- .fd = signal_fd,
- .events = POLLIN,
- },
- [1] = {
.fd = parent_read,
.events = POLLIN,
},
};
int rc = 0;
- sigset_t chldset;
int a = 0; // start index of unprocessed data
int b = 0; // end index of unprocessed data
int sz;
- bool remote_hung = false;
bool found_child = false;
char *btag = basename(tag);
if (!btag) btag = (char*) tag;
- sigemptyset(&chldset);
- sigaddset(&chldset, SIGCHLD);
- pthread_sigmask(SIG_UNBLOCK, &chldset, NULL);
-
while (!found_child) {
- if (TEMP_FAILURE_RETRY(poll(poll_fds, remote_hung ? 1 : 2, -1)) < 0) {
+ if (TEMP_FAILURE_RETRY(poll(poll_fds, ARRAY_SIZE(poll_fds), -1)) < 0) {
ERROR("poll failed\n");
rc = -1;
goto err_poll;
}
- if (!remote_hung) {
- if (poll_fds[1].revents & POLLIN) {
- sz = read(parent_read, &buffer[b], sizeof(buffer) - 1 - b);
+ if (poll_fds[0].revents & POLLIN) {
+ sz = read(parent_read, &buffer[b], sizeof(buffer) - 1 - b);
- sz += b;
- // Log one line at a time
- for (b = 0; b < sz; b++) {
- if (buffer[b] == '\r') {
- buffer[b] = '\0';
- } else if (buffer[b] == '\n') {
- buffer[b] = '\0';
- if (logwrap)
- ALOG(LOG_INFO, btag, "%s", &buffer[a]);
- a = b + 1;
- }
- }
-
- if (a == 0 && b == sizeof(buffer) - 1) {
- // buffer is full, flush
+ sz += b;
+ // Log one line at a time
+ for (b = 0; b < sz; b++) {
+ if (buffer[b] == '\r') {
+ buffer[b] = '\0';
+ } else if (buffer[b] == '\n') {
buffer[b] = '\0';
if (logwrap)
ALOG(LOG_INFO, btag, "%s", &buffer[a]);
- b = 0;
- } else if (a != b) {
- // Keep left-overs
- b -= a;
- memmove(buffer, &buffer[a], b);
- a = 0;
- } else {
- a = 0;
- b = 0;
+ a = b + 1;
}
}
- if (poll_fds[1].revents & POLLHUP) {
- remote_hung = true;
+ if (a == 0 && b == sizeof(buffer) - 1) {
+ // buffer is full, flush
+ buffer[b] = '\0';
+ if (logwrap)
+ ALOG(LOG_INFO, btag, "%s", &buffer[a]);
+ b = 0;
+ } else if (a != b) {
+ // Keep left-overs
+ b -= a;
+ memmove(buffer, &buffer[a], b);
+ a = 0;
+ } else {
+ a = 0;
+ b = 0;
}
}
- if (poll_fds[0].revents & POLLIN) {
- char tmp[32];
+ if (poll_fds[0].revents & POLLHUP) {
int ret;
- read(signal_fd, tmp, sizeof(tmp));
- while (!found_child) {
- ret = TEMP_FAILURE_RETRY(waitpid(-1, &status, WNOHANG));
-
- if (ret <= 0)
- break;
-
- found_child = (pid == ret);
+ ret = waitpid(pid, &status, WNOHANG);
+ if (ret < 0) {
+ rc = errno;
+ ALOG(LOG_ERROR, "logwrap", "waitpid failed with %s\n", strerror(errno));
+ goto err_waitpid;
+ }
+ if (ret > 0) {
+ found_child = true;
}
}
}
@@ -171,6 +152,7 @@
}
}
+err_waitpid:
err_poll:
return rc;
}
@@ -187,23 +169,16 @@
}
}
-static void sigchld_handler(int sig) {
- write(signal_fd_write, &sig, 1);
-}
-
int android_fork_execvp(int argc, char* argv[], int *status, bool ignore_int_quit,
bool logwrap) {
pid_t pid;
int parent_ptty;
int child_ptty;
char *child_devname = NULL;
- struct sigaction chldact;
- struct sigaction oldchldact;
struct sigaction intact;
struct sigaction quitact;
sigset_t blockset;
sigset_t oldset;
- int sockets[2];
int rc = 0;
rc = pthread_mutex_lock(&fd_mutex);
@@ -227,14 +202,21 @@
goto err_ptty;
}
+ child_ptty = open(child_devname, O_RDWR);
+ if (child_ptty < 0) {
+ ERROR("Cannot open child_ptty\n");
+ rc = -1;
+ goto err_child_ptty;
+ }
+
sigemptyset(&blockset);
sigaddset(&blockset, SIGINT);
sigaddset(&blockset, SIGQUIT);
- sigaddset(&blockset, SIGCHLD);
pthread_sigmask(SIG_BLOCK, &blockset, &oldset);
pid = fork();
if (pid < 0) {
+ close(child_ptty);
ERROR("Failed to fork\n");
rc = -1;
goto err_fork;
@@ -243,12 +225,6 @@
pthread_sigmask(SIG_SETMASK, &oldset, NULL);
close(parent_ptty);
- child_ptty = open(child_devname, O_RDWR);
- if (child_ptty < 0) {
- FATAL_CHILD("Problem with child ptty\n");
- return -1;
- }
-
// redirect stdout and stderr
dup2(child_ptty, 1);
dup2(child_ptty, 2);
@@ -256,55 +232,26 @@
child(argc, argv, logwrap);
} else {
- struct sigaction ignact;
-
- memset(&chldact, 0, sizeof(chldact));
- chldact.sa_handler = sigchld_handler;
- chldact.sa_flags = SA_NOCLDSTOP;
-
- sigaction(SIGCHLD, &chldact, &oldchldact);
- if ((!(oldchldact.sa_flags & SA_SIGINFO) &&
- oldchldact.sa_handler != SIG_DFL &&
- oldchldact.sa_handler != SIG_IGN) ||
- ((oldchldact.sa_flags & SA_SIGINFO) &&
- oldchldact.sa_sigaction != NULL)) {
- ALOG(LOG_WARN, "logwrapper", "logwrap replaced the SIGCHLD "
- "handler and might cause interaction issues");
- }
-
+ close(child_ptty);
if (ignore_int_quit) {
+ struct sigaction ignact;
+
memset(&ignact, 0, sizeof(ignact));
ignact.sa_handler = SIG_IGN;
sigaction(SIGINT, &ignact, &intact);
sigaction(SIGQUIT, &ignact, &quitact);
}
- rc = socketpair(AF_UNIX, SOCK_STREAM, 0, sockets);
- if (rc == -1) {
- ERROR("socketpair failed: %s\n", strerror(errno));
- goto err_socketpair;
- }
-
- fcntl(sockets[0], F_SETFD, FD_CLOEXEC);
- fcntl(sockets[0], F_SETFL, O_NONBLOCK);
- fcntl(sockets[1], F_SETFD, FD_CLOEXEC);
- fcntl(sockets[1], F_SETFL, O_NONBLOCK);
-
- signal_fd_write = sockets[0];
-
- rc = parent(argv[0], parent_ptty, sockets[1], pid, status, logwrap);
+ rc = parent(argv[0], parent_ptty, pid, status, logwrap);
}
- close(sockets[0]);
- close(sockets[1]);
-err_socketpair:
if (ignore_int_quit) {
sigaction(SIGINT, &intact, NULL);
sigaction(SIGQUIT, &quitact, NULL);
}
- sigaction(SIGCHLD, &oldchldact, NULL);
err_fork:
pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+err_child_ptty:
err_ptty:
close(parent_ptty);
err_open: