From ee531d949c2f62374fc109252f8cbe61c2b8ee39 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Thu, 4 Apr 2013 17:22:28 +0200 Subject: [PATCH] journal: add public API call sd_journal_get_events() This function should be used when filling in "struct pollfd"'s .events field for watching the journal. It will always return POLLIN for now, but we should keep our options open to change this later on. This mimics libsystemd-bus' sd_bus_get_events() call with the same purpose. --- man/sd_journal_get_fd.xml | 69 +++++++++++++++++++----------- src/journal/journalctl.c | 1 - src/journal/libsystemd-journal.sym | 5 +++ src/journal/sd-journal.c | 13 ++++++ src/systemd/sd-journal.h | 1 + 5 files changed, 64 insertions(+), 25 deletions(-) diff --git a/man/sd_journal_get_fd.xml b/man/sd_journal_get_fd.xml index 3fc9c5f5b5c..e57431ea9e3 100644 --- a/man/sd_journal_get_fd.xml +++ b/man/sd_journal_get_fd.xml @@ -44,6 +44,7 @@ sd_journal_get_fd + sd_journal_get_events sd_journal_reliable_fd sd_journal_process sd_journal_wait @@ -63,6 +64,11 @@ sd_journal* j + + int sd_journal_get_events + sd_journal* j + + int sd_journal_reliable_fd sd_journal* j @@ -87,26 +93,35 @@ sd_journal_get_fd() returns a file descriptor that may be asynchronously polled in - an external event loop and is signaled readable as - soon as the journal changes, because new entries or - files were added, rotation took place, or files have - been deleted, and similar. The file descriptor is - suitable for usage in - poll2 - where it will yield POLLIN on changes. The call takes - one argument: the journal context object. Note that - not all file systems are capable of generating the - necessary events for wakeups from this file descriptor - to be enirely reliable. In particular network files - systems do not generate suitable file change events in - all cases. In such a case an application should not - rely alone on wake-ups from this file descriptor but - wake up and recheck the journal in regular time - intervals, for example every 2s. To detect - cases where this is necessary, use + an external event loop and is signaled as soon as the + journal changes, because new entries or files were + added, rotation took place, or files have been + deleted, and similar. The file descriptor is suitable + for usage in + poll2. Use + sd_journal_get_events() for an + events mask to watch for. The call takes one argument: + the journal context object. Note that not all file + systems are capable of generating the necessary events + for wakeups from this file descriptor to be enirely + reliable. In particular network files systems do not + generate suitable file change events in all cases. In + such a case an application should not rely alone on + wake-ups from this file descriptor but wake up and + recheck the journal in regular time intervals, for + example every 2s. To detect cases where this is + necessary, use sd_journal_reliable_fd(), below. + sd_journal_get_events() + will return the + poll2 + mask to wait for. This function will return a + combination of POLLIN and POLLOUT and similar to fill + into the .events field of + struct pollfd. + sd_journal_reliable_fd() may be used to check whether the wakeup events from the file descriptor returned by @@ -119,15 +134,15 @@ sd_journal_get_fd() are sufficient as only source for wake-ups. - After each POLLIN wake-up + After each poll() wake-up sd_journal_process() needs to be - called to process events and reset the readable state - of the file descriptor. This call will also indicate + called to process events. This call will also indicate what kind of change has been detected (see below; note that spurious wake-ups are possible). A synchronous alternative for using sd_journal_get_fd(), + sd_journal_get_events(), sd_journal_reliable_fd() and sd_journal_process() is sd_journal_wait(). It will @@ -139,17 +154,23 @@ (uint64_t) -1 to wait indefinitely. Internally this call simply combines sd_journal_get_fd(), + sd_journal_get_events(), sd_journal_reliable_fd(), poll() and sd_journal_process() into one. - Return Value - sd_journal_get_fd() returns a valid file descriptor on success or a negative errno-style error + sd_journal_get_fd() returns + a valid file descriptor on success or a negative + errno-style error code. + + sd_journal_get_events() + returns a combination of POLLIN, POLLOUT and suchlike + on success or a negative errno-style error code. sd_journal_reliable_fd() @@ -184,6 +205,7 @@ Notes The sd_journal_get_fd(), + sd_journal_get_events(), sd_journal_reliable_fd(), sd_journal_process() and sd_journal_wait() interfaces are @@ -249,14 +271,13 @@ int main(int argc, char *argv[]) { int wait_for_changes(sd_journal *j) { struct pollfd pollfd; pollfd.fd = sd_journal_get_fd(j); - pollfd.events = POLLIN; + pollfd.events = sd_journal_get_events(j); poll(&pollfd, 1, sd_journal_reliable_fd(j) > 0 ? -1 : 2000); return sd_journal_process(j); } - See Also diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c index 1f26787cf74..86895b8f5b8 100644 --- a/src/journal/journalctl.c +++ b/src/journal/journalctl.c @@ -27,7 +27,6 @@ #include #include #include -#include #include #include #include diff --git a/src/journal/libsystemd-journal.sym b/src/journal/libsystemd-journal.sym index fbe41501f0e..e241318cb03 100644 --- a/src/journal/libsystemd-journal.sym +++ b/src/journal/libsystemd-journal.sym @@ -93,3 +93,8 @@ LIBSYSTEMD_JOURNAL_198 { global: sd_journal_reliable_fd; } LIBSYSTEMD_JOURNAL_196; + +LIBSYSTEMD_JOURNAL_201 { +global: + sd_journal_get_events; +} LIBSYSTEMD_JOURNAL_198; diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c index bb996719347..3eba4cd0d1e 100644 --- a/src/journal/sd-journal.c +++ b/src/journal/sd-journal.c @@ -1981,6 +1981,19 @@ _public_ int sd_journal_get_fd(sd_journal *j) { return j->inotify_fd; } +_public_ int sd_journal_get_events(sd_journal *j) { + int fd; + + if (!j) + return -EINVAL; + + fd = sd_journal_get_fd(j); + if (fd < 0) + return fd; + + return POLLIN; +} + static void process_inotify_event(sd_journal *j, struct inotify_event *e) { Directory *d; int r; diff --git a/src/systemd/sd-journal.h b/src/systemd/sd-journal.h index 2e8d2d882f5..aa7693af70b 100644 --- a/src/systemd/sd-journal.h +++ b/src/systemd/sd-journal.h @@ -127,6 +127,7 @@ int sd_journal_enumerate_unique(sd_journal *j, const void **data, size_t *l); void sd_journal_restart_unique(sd_journal *j); int sd_journal_get_fd(sd_journal *j); +int sd_journal_get_events(sd_journal *j); int sd_journal_reliable_fd(sd_journal *j); int sd_journal_process(sd_journal *j); int sd_journal_wait(sd_journal *j, uint64_t timeout_usec);