From 67d3aade15bede6b162e8bfe88db60311efb0d1f Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Wed, 24 Oct 2018 21:49:52 +0200

Subject: [PATCH] journalctl: in --follow mode watch stdout for POLLHUP/POLLERR

 and exit

Fixes: #9374

(cherry picked from commit 2a1e0f2228bbdfbc18635e959f47df7da50b62fe)

Resolves: #2003236

---

 src/journal/journalctl.c | 65 +++++++++++++++++++++++++++++-----------

 1 file changed, 48 insertions(+), 17 deletions(-)

diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c

index 56b1be530d..fa83dce562 100644

--- a/src/journal/journalctl.c

+++ b/src/journal/journalctl.c

@@ -2064,14 +2064,46 @@ static int sync_journal(void) {

         return send_signal_and_wait(SIGRTMIN+1, "/run/systemd/journal/synced");

 }

-int main(int argc, char *argv[]) {

+static int wait_for_change(sd_journal *j, int poll_fd) {

+        struct pollfd pollfds[] = {

+                { .fd = poll_fd, .events = POLLIN },

+                { .fd = STDOUT_FILENO },

+        };

+

+        struct timespec ts;

+        usec_t timeout;

         int r;

+

+        assert(j);

+        assert(poll_fd >= 0);

+

+        /* Much like sd_journal_wait() but also keeps an eye on STDOUT, and exits as soon as we see a POLLHUP on that,

+         * i.e. when it is closed. */

+

+        r = sd_journal_get_timeout(j, &timeout);

+        if (r < 0)

+                return log_error_errno(r, "Failed to determine journal waiting time: %m");

+

+        if (ppoll(pollfds, ELEMENTSOF(pollfds), timeout == USEC_INFINITY ? NULL : timespec_store(&ts, timeout), NULL) < 0)

+                return log_error_errno(errno, "Couldn't wait for journal event: %m");

+

+        if (pollfds[1].revents & (POLLHUP|POLLERR)) { /* STDOUT has been closed? */

+                log_debug("Standard output has been closed.");

+                return -ECANCELED;

+        }

+

+        r = sd_journal_process(j);

+        if (r < 0)

+                return log_error_errno(r, "Failed to process journal events: %m");

+

+        return 0;

+}

+

+int main(int argc, char *argv[]) {

+        bool previous_boot_id_valid = false, first_line = true, ellipsized = false, need_seek = false;

         _cleanup_(sd_journal_closep) sd_journal *j = NULL;

-        bool need_seek = false;

         sd_id128_t previous_boot_id;

-        bool previous_boot_id_valid = false, first_line = true;

-        int n_shown = 0;

-        bool ellipsized = false;

+        int n_shown = 0, r, poll_fd = -1;

         setlocale(LC_ALL, "");

         log_parse_environment();

@@ -2391,15 +2423,15 @@ int main(int argc, char *argv[]) {

         /* Opening the fd now means the first sd_journal_wait() will actually wait */

         if (arg_follow) {

-                r = sd_journal_get_fd(j);

-                if (r == -EMFILE) {

-                        log_warning("Insufficent watch descriptors available. Reverting to -n.");

+                poll_fd = sd_journal_get_fd(j);

+                if (poll_fd == -EMFILE) {

+                        log_warning_errno(poll_fd, "Insufficent watch descriptors available. Reverting to -n.");

                         arg_follow = false;

-                } else if (r == -EMEDIUMTYPE) {

-                        log_error_errno(r, "The --follow switch is not supported in conjunction with reading from STDIN.");

+                } else if (poll_fd == -EMEDIUMTYPE) {

+                        log_error_errno(poll_fd, "The --follow switch is not supported in conjunction with reading from STDIN.");

                         goto finish;

-                } else if (r < 0) {

-                        log_error_errno(r, "Failed to get journal fd: %m");

+                } else if (poll_fd < 0) {

+                        log_error_errno(poll_fd, "Failed to get journal fd: %m");

                         goto finish;

                 }

         }

@@ -2621,7 +2653,7 @@ int main(int argc, char *argv[]) {

                         need_seek = true;

                         if (r == -EADDRNOTAVAIL)

                                 break;

-                        else if (r < 0 || ferror(stdout))

+                        else if (r < 0)

                                 goto finish;

                         n_shown++;

@@ -2659,11 +2691,10 @@ int main(int argc, char *argv[]) {

                 }

                 fflush(stdout);

-                r = sd_journal_wait(j, (uint64_t) -1);

-                if (r < 0) {

-                        log_error_errno(r, "Couldn't wait for journal event: %m");

+

+                r = wait_for_change(j, poll_fd);

+                if (r < 0)

                         goto finish;

-                }

                 first_line = false;

         }