Ensure vold doesn't hang when a child process dies
Add a monitoring thread that notifies the main parent thread when the child
process terminates. The return code from the child is then propagated back up
to the parent.
Change-Id: Idf46e100e8dee2e8f1aaa331317f3c4955632183
diff --git a/logwrapper.c b/logwrapper.c
index 6e47cb8..e8a90e6 100644
--- a/logwrapper.c
+++ b/logwrapper.c
@@ -15,6 +15,8 @@
*/
#include <string.h>
+#include <sys/select.h>
+#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
@@ -22,75 +24,93 @@
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
+#include <pthread.h>
#include "private/android_filesystem_config.h"
#include "cutils/log.h"
#include "cutils/sched_policy.h"
-int parent(const char *tag, int parent_read) {
+struct monitor_data {
+ const char *tag;
+ int fd;
+};
+
+static int parent(const char *tag, int parent_read, int monitor_read) {
int status;
char buffer[4096];
+ fd_set fds;
+ int maxfd;
+ int rc = -EAGAIN;
int a = 0; // start index of unprocessed data
int b = 0; // end index of unprocessed data
int sz;
- while ((sz = read(parent_read, &buffer[b], sizeof(buffer) - 1 - b)) > 0) {
- 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';
+ maxfd = 1 + (parent_read > monitor_read ? parent_read : monitor_read);
+ do {
+ FD_ZERO(&fds);
+ FD_SET(parent_read, &fds);
+ FD_SET(monitor_read, &fds);
+
+ if (select(maxfd, &fds, NULL, NULL, NULL) <= 0) {
+ ALOG(LOG_INFO, "logwrapper", "select failed");
+ break;
+ }
+
+ if (FD_ISSET(parent_read, &fds)) {
+ 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';
+
+ ALOG(LOG_INFO, tag, "%s", &buffer[a]);
+ a = b + 1;
+ }
+ }
+
+ if (a == 0 && b == sizeof(buffer) - 1) {
+ // buffer is full, flush
+ buffer[b] = '\0';
ALOG(LOG_INFO, tag, "%s", &buffer[a]);
- a = b + 1;
+ b = 0;
+ } else if (a != b) {
+ // Keep left-overs
+ b -= a;
+ memmove(buffer, &buffer[a], b);
+ a = 0;
+ } else {
+ a = 0;
+ b = 0;
}
}
- if (a == 0 && b == sizeof(buffer) - 1) {
- // buffer is full, flush
- buffer[b] = '\0';
- ALOG(LOG_INFO, tag, "%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;
+ // Child exited, get return status and exit loop
+ if (FD_ISSET(monitor_read, &fds)) {
+ if (read(monitor_read, &rc, sizeof(rc)) != sizeof(rc)) {
+ ALOG(LOG_ERROR, "logwrapper", "Unable to read child return "
+ "status");
+ rc = -ECHILD;
+ }
+ break;
}
+ } while (1);
- }
// Flush remaining data
if (a != b) {
buffer[b] = '\0';
ALOG(LOG_INFO, tag, "%s", &buffer[a]);
}
- status = 0xAAAA;
- if (wait(&status) != -1) { // Wait for child
- if (WIFEXITED(status)) {
- if (WEXITSTATUS(status) != 0) {
- ALOG(LOG_INFO, "logwrapper", "%s terminated by exit(%d)", tag,
- WEXITSTATUS(status));
- }
- return WEXITSTATUS(status);
- } else if (WIFSIGNALED(status))
- ALOG(LOG_INFO, "logwrapper", "%s terminated by signal %d", tag,
- WTERMSIG(status));
- else if (WIFSTOPPED(status))
- ALOG(LOG_INFO, "logwrapper", "%s stopped by signal %d", tag,
- WSTOPSIG(status));
- } else
- ALOG(LOG_INFO, "logwrapper", "%s wait() failed: %s (%d)", tag,
- strerror(errno), errno);
- return -EAGAIN;
+
+ return rc;
}
-void child(int argc, const char**argv) {
+static void child(int argc, const char**argv) {
// create null terminated argv_child array
char* argv_child[argc + 1];
memcpy(argv_child, argv, argc * sizeof(char *));
@@ -104,6 +124,33 @@
}
}
+static void *monitor(void *arg)
+{
+ struct monitor_data *data = arg;
+ int status;
+ int rc = -EAGAIN;
+
+ if (wait(&status) != -1) { // Wait for child
+ if (WIFEXITED(status)) {
+ if (WEXITSTATUS(status) != 0) {
+ ALOG(LOG_INFO, "logwrapper", "%s terminated by exit(%d)",
+ data->tag, WEXITSTATUS(status));
+ }
+ rc = WEXITSTATUS(status);
+ } else if (WIFSIGNALED(status))
+ ALOG(LOG_INFO, "logwrapper", "%s terminated by signal %d",
+ data->tag, WTERMSIG(status));
+ else if (WIFSTOPPED(status))
+ ALOG(LOG_INFO, "logwrapper", "%s stopped by signal %d", data->tag,
+ WSTOPSIG(status));
+ } else
+ ALOG(LOG_INFO, "logwrapper", "%s wait() failed: %s (%d)", data->tag,
+ strerror(errno), errno);
+
+ write(data->fd, &rc, sizeof(rc));
+ return NULL;
+}
+
int logwrap(int argc, const char* argv[], int background)
{
pid_t pid;
@@ -135,15 +182,14 @@
/*
* Child
*/
+ close(parent_ptty);
child_ptty = open(child_devname, O_RDWR);
if (child_ptty < 0) {
- close(parent_ptty);
ALOG(LOG_ERROR, "logwrapper", "Problem with child ptty");
_exit(-errno);
}
// redirect stdout and stderr
- close(parent_ptty);
dup2(child_ptty, 1);
dup2(child_ptty, 2);
close(child_ptty);
@@ -161,8 +207,29 @@
/*
* Parent
*/
- int rc = parent(argv[0], parent_ptty);
+ int rc, err;
+ int sockets[2];
+ pthread_t thread_id;
+ struct monitor_data data;
+
+ if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets)) {
+ err = errno;
+ ALOG(LOG_ERROR, "logwrapper", "Unable to create monitoring "
+ "socket: %s (%d)", strerror(err), err);
+ exit(-err);
+ }
+ data.tag = argv[0];
+ data.fd = sockets[1];
+ err = pthread_create(&thread_id, NULL, monitor, &data);
+ if (err != 0) {
+ ALOG(LOG_ERROR, "logwrapper", "Unable to create monitoring "
+ "thread: %s (%d)", strerror(err), err);
+ exit(-err);
+ }
+ rc = parent(argv[0], parent_ptty, sockets[0]);
close(parent_ptty);
+ close(sockets[0]);
+ close(sockets[1]);
return rc;
}
