Use only one global variable for snapshot creation pids.

There's no need to have pre_create_hook_pid, rsync_pid and
post_create_hook_pid because only one of them can be running at
any point in time. We can always tell which it is by examining the
snapshot_creation_status.

So replace these three variables by the single create_pid variable.

Besides of killing two global variables, this change also fixes a
real bug: If the dss process catches SIGINT or SIGTERM, the old code
would only kill a running rsync process but not the pre-create or
post-create hook. However, the new code kills whatever create process
is currently running, which is the right thing to do.

diff --git a/dss.c b/dss.c
index ad62c3c04bdb1f937b41d07a860a0007589e3fe4..fd876e5ddc1d340dec79dee84f9706dc9a09912f 100644 (file)
--- a/dss.c
+++ b/dss.c
@@ -40,18 +40,14 @@ static struct gengetopt_args_info conf;
 static FILE *logfile;
 /** The read end of the signal pipe */
 static int signal_pipe;
-/** Process id of current rsync process. */
-static pid_t rsync_pid;
-/** Whether the rsync process is currently stopped */
-static int rsync_stopped;
+/** Process id of current pre-create-hook/rsync/post-create-hook process. */
+static pid_t create_pid;
+/** Whether the pre-create-hook/rsync/post-create-hook is currently stopped. */
+static int create_process_stopped;
 /** Process id of current rm process. */
 static pid_t rm_pid;
 /** When the next snapshot is due. */
 static struct timeval next_snapshot_time;
-/** The pid of the pre-create hook. */
-static pid_t pre_create_hook_pid;
-/** The pid of the post-create hook. */
-static pid_t post_create_hook_pid;
 /** Creation time of the snapshot currently being created. */
 static int64_t current_snapshot_creation_time;
 /** Needed by the post-create hook. */
@@ -372,7 +368,7 @@ static int pre_create_hook(void)
                return 0;
        }
        DSS_NOTICE_LOG("executing %s\n", conf.pre_create_hook_arg);
-       ret = dss_exec_cmdline_pid(&pre_create_hook_pid,
+       ret = dss_exec_cmdline_pid(&create_pid,
                conf.pre_create_hook_arg, fds);
        if (ret < 0)
                return ret;
@@ -393,7 +389,7 @@ static int post_create_hook(void)
        cmd = make_message("%s %s/%s", conf.post_create_hook_arg,
                conf.dest_dir_arg, path_to_last_complete_snapshot);
        DSS_NOTICE_LOG("executing %s\n", cmd);
-       ret = dss_exec_cmdline_pid(&post_create_hook_pid, cmd, fds);
+       ret = dss_exec_cmdline_pid(&create_pid, cmd, fds);
        free(cmd);
        if (ret < 0)
                return ret;
@@ -409,23 +405,22 @@ static void kill_process(pid_t pid)
        kill(pid, SIGTERM);
 }
 
-static void stop_rsync_process(void)
+static void stop_create_process(void)
 {
-       if (!rsync_pid || rsync_stopped)
+       if (!create_pid || create_process_stopped)
                return;
-       kill(SIGSTOP, rsync_pid);
-       rsync_stopped = 1;
+       kill(SIGSTOP, create_pid);
+       create_process_stopped = 1;
 }
 
-static void restart_rsync_process(void)
+static void restart_create_process(void)
 {
-       if (!rsync_pid || !rsync_stopped)
+       if (!create_pid || !create_process_stopped)
                return;
-       kill (SIGCONT, rsync_pid);
-       rsync_stopped = 0;
+       kill (SIGCONT, create_pid);
+       create_process_stopped = 0;
 }
 
-
 /**
  * Print a log message about the exit status of a child.
  */
@@ -501,7 +496,7 @@ static int handle_rsync_exit(int status)
        int es, ret;
 
        if (!WIFEXITED(status)) {
-               DSS_ERROR_LOG("rsync process %d died involuntary\n", (int)rsync_pid);
+               DSS_ERROR_LOG("rsync process %d died involuntary\n", (int)create_pid);
                ret = -E_INVOLUNTARY_EXIT;
                snapshot_creation_status = SCS_READY;
                compute_next_snapshot_time();
@@ -510,7 +505,7 @@ static int handle_rsync_exit(int status)
        es = WEXITSTATUS(status);
        if (es == 13) { /* Errors with program diagnostics */
                DSS_WARNING_LOG("rsync process %d returned %d -- restarting\n",
-                       (int)rsync_pid, es);
+                       (int)create_pid, es);
                snapshot_creation_status = SCS_RSYNC_NEEDS_RESTART;
                gettimeofday(&next_snapshot_time, NULL);
                next_snapshot_time.tv_sec += 60;
@@ -518,7 +513,7 @@ static int handle_rsync_exit(int status)
                goto out;
        }
        if (es != 0 && es != 23 && es != 24) {
-               DSS_ERROR_LOG("rsync process %d returned %d\n", (int)rsync_pid, es);
+               DSS_ERROR_LOG("rsync process %d returned %d\n", (int)create_pid, es);
                ret = -E_BAD_EXIT_CODE;
                snapshot_creation_status = SCS_READY;
                compute_next_snapshot_time();
@@ -529,8 +524,8 @@ static int handle_rsync_exit(int status)
                goto out;
        snapshot_creation_status = SCS_RSYNC_SUCCESS;
 out:
-       rsync_pid = 0;
-       rsync_stopped = 0;
+       create_pid = 0;
+       create_process_stopped = 0;
        return ret;
 }
 
@@ -554,7 +549,7 @@ static int handle_pre_create_hook_exit(int status)
        snapshot_creation_status = SCS_PRE_HOOK_SUCCESS;
        ret = 1;
 out:
-       pre_create_hook_pid = 0;
+       create_pid = 0;
        return ret;
 }
 
@@ -565,17 +560,25 @@ static int handle_sigchld(void)
 
        if (ret <= 0)
                return ret;
-       if (pid == rsync_pid)
-               return handle_rsync_exit(status);
+
+       if (pid == create_pid) {
+               switch (snapshot_creation_status) {
+               case SCS_PRE_HOOK_RUNNING:
+                       return handle_pre_create_hook_exit(status);
+               case SCS_RSYNC_RUNNING:
+                       return handle_rsync_exit(status);
+               case SCS_POST_HOOK_RUNNING:
+                       snapshot_creation_status = SCS_READY;
+                       compute_next_snapshot_time();
+                       return 1;
+               default:
+                       DSS_EMERG_LOG("BUG: create can't die in status %d\n",
+                               snapshot_creation_status);
+                       return -E_BUG;
+               }
+       }
        if (pid == rm_pid)
                return handle_rm_exit(status);
-       if (pid == pre_create_hook_pid)
-               return handle_pre_create_hook_exit(status);
-       if (pid == post_create_hook_pid) {
-               snapshot_creation_status = SCS_READY;
-               compute_next_snapshot_time();
-               return 1;
-       }
        DSS_EMERG_LOG("BUG: unknown process %d died\n", (int)pid);
        return -E_BUG;
 }
@@ -696,8 +699,8 @@ static int handle_signal(void)
        switch (sig) {
        case SIGINT:
        case SIGTERM:
-               restart_rsync_process();
-               kill_process(rsync_pid);
+               restart_create_process();
+               kill_process(create_pid);
                kill_process(rm_pid);
                ret = -E_SIGNAL;
                break;
@@ -785,7 +788,7 @@ static int create_snapshot(char **argv)
        name = incomplete_name(current_snapshot_creation_time);
        DSS_NOTICE_LOG("creating new snapshot %s\n", name);
        free(name);
-       ret = dss_exec(&rsync_pid, argv[0], argv, fds);
+       ret = dss_exec(&create_pid, argv[0], argv, fds);
        if (ret < 0)
                return ret;
        snapshot_creation_status = SCS_RSYNC_RUNNING;
@@ -832,10 +835,10 @@ static int select_loop(void)
                if (ret < 0)
                        goto out;
                if (rm_pid) {
-                       stop_rsync_process();
+                       stop_create_process();
                        continue;
                }
-               restart_rsync_process();
+               restart_create_process();
                gettimeofday(&now, NULL);
                if (tv_diff(&next_snapshot_time, &now, NULL) > 0)
                        continue;
@@ -967,8 +970,8 @@ static int com_create(void)
        ret = pre_create_hook();
        if (ret < 0)
                return ret;
-       if (pre_create_hook_pid) {
-               ret = wait_for_process(pre_create_hook_pid, &status);
+       if (create_pid) {
+               ret = wait_for_process(create_pid, &status);
                if (ret < 0)
                        return ret;
                ret = handle_pre_create_hook_exit(status);
@@ -979,15 +982,15 @@ static int com_create(void)
        ret = create_snapshot(rsync_argv);
        if (ret < 0)
                goto out;
-       ret = wait_for_process(rsync_pid, &status);
+       ret = wait_for_process(create_pid, &status);
        if (ret < 0)
                goto out;
        ret = handle_rsync_exit(status);
        if (ret < 0)
                goto out;
        post_create_hook();
-       if (post_create_hook_pid)
-               ret = wait_for_process(post_create_hook_pid, &status);
+       if (create_pid)
+               ret = wait_for_process(create_pid, &status);
 out:
        free_rsync_argv(rsync_argv);
        return ret;