core: allow PIDs to be watched by two units at the same time
In some cases it is interesting to map a PID to two units at the same time. For example, when a user logs in via a getty, which is reexeced to /sbin/login that binary will be explicitly referenced as main pid of the getty service, as well as implicitly referenced as part of the session scope.
This commit is contained in:
Lennart Poettering
parent
8190da36f7
commit
5ba6985b6c
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@ -447,10 +447,6 @@ int manager_new(SystemdRunningAs running_as, Manager **_m) {
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if (r < 0)
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goto fail;
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r = hashmap_ensure_allocated(&m->watch_pids, trivial_hash_func, trivial_compare_func);
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if (r < 0)
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goto fail;
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r = hashmap_ensure_allocated(&m->watch_bus, string_hash_func, string_compare_func);
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if (r < 0)
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goto fail;
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@ -778,7 +774,8 @@ void manager_free(Manager *m) {
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hashmap_free(m->units);
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hashmap_free(m->jobs);
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hashmap_free(m->watch_pids);
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hashmap_free(m->watch_pids1);
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hashmap_free(m->watch_pids2);
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hashmap_free(m->watch_bus);
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sd_event_source_unref(m->signal_event_source);
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@ -1319,6 +1316,26 @@ static unsigned manager_dispatch_dbus_queue(Manager *m) {
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return n;
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}
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static void manager_invoke_notify_message(Manager *m, Unit *u, pid_t pid, char *buf, size_t n) {
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_cleanup_strv_free_ char **tags = NULL;
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assert(m);
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assert(u);
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assert(buf);
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assert(n > 0);
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tags = strv_split(buf, "\n\r");
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if (!tags) {
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log_oom();
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return;
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}
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log_debug_unit(u->id, "Got notification message for unit %s", u->id);
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if (UNIT_VTABLE(u)->notify_message)
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UNIT_VTABLE(u)->notify_message(u, pid, tags);
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}
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static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
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Manager *m = userdata;
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ssize_t n;
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@ -1337,6 +1354,7 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
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.iov_base = buf,
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.iov_len = sizeof(buf)-1,
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};
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bool found = false;
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union {
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struct cmsghdr cmsghdr;
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@ -1351,7 +1369,6 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
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};
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struct ucred *ucred;
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Unit *u;
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_cleanup_strv_free_ char **tags = NULL;
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n = recvmsg(m->notify_fd, &msghdr, MSG_DONTWAIT);
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if (n <= 0) {
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@ -1374,36 +1391,50 @@ static int manager_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t
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ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
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u = hashmap_get(m->watch_pids, LONG_TO_PTR(ucred->pid));
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if (!u) {
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u = manager_get_unit_by_pid(m, ucred->pid);
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if (!u) {
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log_warning("Cannot find unit for notify message of PID "PID_FMT".", ucred->pid);
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continue;
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}
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}
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assert((size_t) n < sizeof(buf));
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buf[n] = 0;
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tags = strv_split(buf, "\n\r");
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if (!tags)
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return log_oom();
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log_debug_unit(u->id, "Got notification message for unit %s", u->id);
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u = manager_get_unit_by_pid(m, ucred->pid);
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if (u) {
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manager_invoke_notify_message(m, u, ucred->pid, buf, n);
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found = true;
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}
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if (UNIT_VTABLE(u)->notify_message)
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UNIT_VTABLE(u)->notify_message(u, ucred->pid, tags);
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u = hashmap_get(m->watch_pids1, LONG_TO_PTR(ucred->pid));
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if (u) {
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manager_invoke_notify_message(m, u, ucred->pid, buf, n);
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found = true;
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}
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u = hashmap_get(m->watch_pids2, LONG_TO_PTR(ucred->pid));
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if (u) {
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manager_invoke_notify_message(m, u, ucred->pid, buf, n);
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found = true;
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}
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if (!found)
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log_warning("Cannot find unit for notify message of PID "PID_FMT".", ucred->pid);
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}
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return 0;
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}
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static void invoke_sigchld_event(Manager *m, Unit *u, siginfo_t *si) {
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assert(m);
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assert(u);
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assert(si);
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log_debug_unit(u->id, "Child "PID_FMT" belongs to %s", si->si_pid, u->id);
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unit_unwatch_pid(u, si->si_pid);
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UNIT_VTABLE(u)->sigchld_event(u, si->si_pid, si->si_code, si->si_status);
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}
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static int manager_dispatch_sigchld(Manager *m) {
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assert(m);
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for (;;) {
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siginfo_t si = {};
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Unit *u;
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/* First we call waitd() for a PID and do not reap the
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* zombie. That way we can still access /proc/$PID for
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@ -1424,15 +1455,30 @@ static int manager_dispatch_sigchld(Manager *m) {
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if (si.si_code == CLD_EXITED || si.si_code == CLD_KILLED || si.si_code == CLD_DUMPED) {
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_cleanup_free_ char *name = NULL;
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Unit *u;
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get_process_comm(si.si_pid, &name);
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log_debug("Got SIGCHLD for process "PID_FMT" (%s)", si.si_pid, strna(name));
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}
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/* And now figure out the unit this belongs to */
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u = hashmap_get(m->watch_pids, LONG_TO_PTR(si.si_pid));
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if (!u)
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log_debug("Child "PID_FMT" (%s) died (code=%s, status=%i/%s)",
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si.si_pid, strna(name),
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sigchld_code_to_string(si.si_code),
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si.si_status,
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strna(si.si_code == CLD_EXITED
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? exit_status_to_string(si.si_status, EXIT_STATUS_FULL)
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: signal_to_string(si.si_status)));
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/* And now figure out the unit this belongs
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* to, it might be multiple... */
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u = manager_get_unit_by_pid(m, si.si_pid);
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if (u)
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invoke_sigchld_event(m, u, &si);
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u = hashmap_get(m->watch_pids1, LONG_TO_PTR(si.si_pid));
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if (u)
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invoke_sigchld_event(m, u, &si);
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u = hashmap_get(m->watch_pids2, LONG_TO_PTR(si.si_pid));
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if (u)
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invoke_sigchld_event(m, u, &si);
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}
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/* And now, we actually reap the zombie. */
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if (waitid(P_PID, si.si_pid, &si, WEXITED) < 0) {
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@ -1441,26 +1487,6 @@ static int manager_dispatch_sigchld(Manager *m) {
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return -errno;
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}
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if (si.si_code != CLD_EXITED && si.si_code != CLD_KILLED && si.si_code != CLD_DUMPED)
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continue;
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log_debug("Child %lu died (code=%s, status=%i/%s)",
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(long unsigned) si.si_pid,
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sigchld_code_to_string(si.si_code),
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si.si_status,
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strna(si.si_code == CLD_EXITED
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? exit_status_to_string(si.si_status, EXIT_STATUS_FULL)
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: signal_to_string(si.si_status)));
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if (!u)
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continue;
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log_debug_unit(u->id,
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"Child %lu belongs to %s", (long unsigned) si.si_pid, u->id);
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unit_unwatch_pid(u, si.si_pid);
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UNIT_VTABLE(u)->sigchld_event(u, si.si_pid, si.si_code, si.si_status);
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}
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return 0;
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@ -96,7 +96,14 @@ struct Manager {
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sd_event *event;
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Hashmap *watch_pids; /* pid => Unit object n:1 */
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/* We use two hash tables here, since the same PID might be
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* watched by two different units: once the unit that forked
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* it off, and possibly a different unit to which it was
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* joined as cgroup member. Since we know that it is either
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* one or two units for each PID we just use to hashmaps
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* here. */
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Hashmap *watch_pids1; /* pid => Unit object n:1 */
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Hashmap *watch_pids2; /* pid => Unit object n:1 */
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sd_event_source *run_queue_event_source;
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@ -1704,16 +1704,27 @@ int unit_watch_pid(Unit *u, pid_t pid) {
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assert(u);
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assert(pid >= 1);
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/* Watch a specific PID. We only support one or two units
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* watching each PID for now, not more. */
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r = hashmap_ensure_allocated(&u->manager->watch_pids1, trivial_hash_func, trivial_compare_func);
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if (r < 0)
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return r;
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r = set_ensure_allocated(&u->pids, trivial_hash_func, trivial_compare_func);
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if (r < 0)
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return r;
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/* Watch a specific PID. We only support one unit watching
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* each PID for now. */
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r = hashmap_put(u->manager->watch_pids1, LONG_TO_PTR(pid), u);
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if (r == -EEXIST) {
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r = hashmap_ensure_allocated(&u->manager->watch_pids2, trivial_hash_func, trivial_compare_func);
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if (r < 0)
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return r;
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r = set_put(u->pids, LONG_TO_PTR(pid));
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r = hashmap_put(u->manager->watch_pids2, LONG_TO_PTR(pid), u);
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}
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q = hashmap_put(u->manager->watch_pids, LONG_TO_PTR(pid), u);
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q = set_put(u->pids, LONG_TO_PTR(pid));
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if (q < 0)
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return q;
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@ -1724,7 +1735,8 @@ void unit_unwatch_pid(Unit *u, pid_t pid) {
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assert(u);
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assert(pid >= 1);
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hashmap_remove_value(u->manager->watch_pids, LONG_TO_PTR(pid), u);
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hashmap_remove_value(u->manager->watch_pids1, LONG_TO_PTR(pid), u);
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hashmap_remove_value(u->manager->watch_pids2, LONG_TO_PTR(pid), u);
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set_remove(u->pids, LONG_TO_PTR(pid));
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}
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@ -1797,8 +1809,10 @@ void unit_unwatch_all_pids(Unit *u) {
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assert(u);
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SET_FOREACH(e, u->pids, i)
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hashmap_remove_value(u->manager->watch_pids, e, u);
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SET_FOREACH(e, u->pids, i) {
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hashmap_remove_value(u->manager->watch_pids1, e, u);
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hashmap_remove_value(u->manager->watch_pids2, e, u);
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}
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set_free(u->pids);
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u->pids = NULL;
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