man: add notes about thread safety of sd_journal_* functions

Fixes #4056.

14 files changed, 66 insertions, 3 deletions

diff --git a/man/sd-journal.xml b/man/sd-journal.xml
index 936a83acf7..0f4b3e8eea 100644
--- a/man/sd-journal.xml
+++ b/man/sd-journal.xml
@@ -98,6 +98,21 @@
     tool.</para>
   </refsect1>
 
+  <refsect1>
+    <title>Thread safety</title>
+
+    <para>Functions that operate on the <structname>sd_journal</structname> object are thread
+    agnostic — given <structname>sd_journal</structname> pointer may only be used from one thread at
+    a time, but multiple threads may use multiple such objects safely. Other functions —
+    those that are used to send entries to the journal, like
+    <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    and similar, or those that are used to retrieve global information like
+    <citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    and
+    <citerefentry><refentrytitle>sd_journal_get_catalog_for_message_id</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    — are thread-safe and may be called from multiple threads in parallel.</para>
+  </refsect1>
+
   <xi:include href="libsystemd-pkgconfig.xml" />
 
   <refsect1>
diff --git a/man/sd_journal_add_match.xml b/man/sd_journal_add_match.xml
index 98415d53fd..7c64329aed 100644
--- a/man/sd_journal_add_match.xml
+++ b/man/sd_journal_add_match.xml
@@ -168,6 +168,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_add_match()</function>,
     <function>sd_journal_add_disjunction()</function>,
     <function>sd_journal_add_conjunction()</function> and
diff --git a/man/sd_journal_enumerate_fields.xml b/man/sd_journal_enumerate_fields.xml
index fa5884106b..bc2c21ed4b 100644
--- a/man/sd_journal_enumerate_fields.xml
+++ b/man/sd_journal_enumerate_fields.xml
@@ -110,6 +110,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_enumerate_fields()</function> and <function>sd_journal_restart_fields()</function>
     interfaces are available as a shared library, which can be compiled and linked to with the
     <constant>libsystemd</constant> <citerefentry
diff --git a/man/sd_journal_get_catalog.xml b/man/sd_journal_get_catalog.xml
index c19eb11b20..35ec46f63e 100644
--- a/man/sd_journal_get_catalog.xml
+++ b/man/sd_journal_get_catalog.xml
@@ -112,6 +112,10 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>Function <function>sd_journal_get_catalog()</function> is thread-agnostic and only a
+    single thread may operate on a given <structname>sd_journal</structname> object. Function
+    <function>sd_journal_get_catalog_for_message_id() is thread-safe.</function></para>
+
     <para>The <function>sd_journal_get_catalog()</function> and
     <function>sd_journal_get_catalog_for_message_id()</function>
     interfaces are available as a shared library, which can be
diff --git a/man/sd_journal_get_cursor.xml b/man/sd_journal_get_cursor.xml
index a400d8b1b5..b7aa05f8b2 100644
--- a/man/sd_journal_get_cursor.xml
+++ b/man/sd_journal_get_cursor.xml
@@ -122,6 +122,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_get_cursor()</function> and
     <function>sd_journal_test_cursor()</function> interfaces are
     available as a shared library, which can be compiled and linked to
diff --git a/man/sd_journal_get_cutoff_realtime_usec.xml b/man/sd_journal_get_cutoff_realtime_usec.xml
index 23e7cc65e8..0950e11b44 100644
--- a/man/sd_journal_get_cutoff_realtime_usec.xml
+++ b/man/sd_journal_get_cutoff_realtime_usec.xml
@@ -120,6 +120,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The
     <function>sd_journal_get_cutoff_realtime_usec()</function> and
     <function>sd_journal_get_cutoff_monotonic_usec()</function>
diff --git a/man/sd_journal_get_usage.xml b/man/sd_journal_get_usage.xml
index 72c804d834..06b0ff534d 100644
--- a/man/sd_journal_get_usage.xml
+++ b/man/sd_journal_get_usage.xml
@@ -80,6 +80,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_get_usage()</function> interface is
     available as a shared library, which can be compiled and linked to
     with the
diff --git a/man/sd_journal_has_runtime_files.xml b/man/sd_journal_has_runtime_files.xml
index 237e649206..3f6d56ca77 100644
--- a/man/sd_journal_has_runtime_files.xml
+++ b/man/sd_journal_has_runtime_files.xml
@@ -86,6 +86,18 @@
   </refsect1>
 
   <refsect1>
+    <title>Notes</title>
+
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
+    <para>Functions listed here are available as a shared library, which can be compiled and linked
+    to with the <constant>libsystemd</constant> <citerefentry
+    project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    file.</para>
+  </refsect1>
+
+  <refsect1>
     <title>See Also</title>
     <para>
       <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
diff --git a/man/sd_journal_next.xml b/man/sd_journal_next.xml
index 115fe26661..7c385de260 100644
--- a/man/sd_journal_next.xml
+++ b/man/sd_journal_next.xml
@@ -146,6 +146,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_next()</function>,
     <function>sd_journal_previous()</function>,
     <function>sd_journal_next_skip()</function> and
diff --git a/man/sd_journal_open.xml b/man/sd_journal_open.xml
index 74e67023b5..25b3048f2e 100644
--- a/man/sd_journal_open.xml
+++ b/man/sd_journal_open.xml
@@ -208,6 +208,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_open()</function>,
     <function>sd_journal_open_directory()</function> and
     <function>sd_journal_close()</function> interfaces are available
diff --git a/man/sd_journal_print.xml b/man/sd_journal_print.xml
index 76542527fc..2d8dd635aa 100644
--- a/man/sd_journal_print.xml
+++ b/man/sd_journal_print.xml
@@ -201,9 +201,10 @@ sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(
   </refsect1>
 
   <refsect1>
-    <title>Async signal safety</title>
-    <para><function>sd_journal_sendv()</function> is "async signal
-    safe" in the meaning of
+    <title>Thread safety</title>
+    <para>All functions listed here are thread-safe and may be called in parallel from multiple threads.</para>
+
+    <para><function>sd_journal_sendv()</function> is "async signal safe" in the meaning of
     <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
     </para>
 
diff --git a/man/sd_journal_query_unique.xml b/man/sd_journal_query_unique.xml
index dbff55c105..d7a41a039c 100644
--- a/man/sd_journal_query_unique.xml
+++ b/man/sd_journal_query_unique.xml
@@ -150,6 +150,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_query_unique()</function>,
     <function>sd_journal_enumerate_unique()</function> and
     <function>sd_journal_restart_unique()</function> interfaces are
diff --git a/man/sd_journal_seek_head.xml b/man/sd_journal_seek_head.xml
index d74c2d5bbc..985073496c 100644
--- a/man/sd_journal_seek_head.xml
+++ b/man/sd_journal_seek_head.xml
@@ -144,6 +144,9 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>All functions listed here are thread-agnostic and only a single thread may operate
+    on a given <structname>sd_journal</structname> object.</para>
+
     <para>The <function>sd_journal_seek_head()</function>,
     <function>sd_journal_seek_tail()</function>,
     <function>sd_journal_seek_monotonic_usec()</function>,
diff --git a/man/sd_journal_stream_fd.xml b/man/sd_journal_stream_fd.xml
index 2ea7731b48..226298ae1b 100644
--- a/man/sd_journal_stream_fd.xml
+++ b/man/sd_journal_stream_fd.xml
@@ -104,6 +104,10 @@
   <refsect1>
     <title>Notes</title>
 
+    <para>Function <function>sd_journal_stream_fd()</function> is thread-safe and may be be called
+    from multiple threads. All calls will return the same file descriptor, although temporarily
+    multiple file descriptors may be open.</para>
+
     <para>The <function>sd_journal_stream_fd()</function> interface is
     available as a shared library, which can be compiled and linked to
     with the