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authorZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2014-10-21 18:44:09 -0400
committerZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2014-10-23 00:17:18 -0400
commita9becdd65bb4b64675bc0c109d14ab12b1ecd2b7 (patch)
tree45faa8c9e120afe1e8227926bc238d5e0eeb2920
parent203af57fcdced5debfc26e1083eaefa031e322f4 (diff)
sd-daemon,man: ignore missing $WATCHDOG_PID
Systemd 209 started setting $WATCHDOG_PID, and sd-daemon watch was modified to check for this variable. This means that sd_watchdog_enabled() stopped working with previous versions of systemd. But sd-event is a public library and API and we must keep it working even when a program compiled with a newer version of the libary is used on a system running an older version of the manager. getenv() and unsetenv() are fairly expensive calls, so optimize sd_watchdog_enabled() by not calling them when unnecessary. man: centralize the description of $WATCHDOG_PID and $WATCHDOG_USEC in the sd_watchdog_enabled manpage. It is better not to repeat the same stuff in two places.
-rw-r--r--man/sd_notify.xml15
-rw-r--r--man/sd_watchdog_enabled.xml53
-rw-r--r--src/libsystemd/sd-daemon/sd-daemon.c48
3 files changed, 63 insertions, 53 deletions
diff --git a/man/sd_notify.xml b/man/sd_notify.xml
index fbb882dfd2..35f6f71ab3 100644
--- a/man/sd_notify.xml
+++ b/man/sd_notify.xml
@@ -192,17 +192,12 @@
<varname>WatchdogSec=</varname> is
enabled for it. See
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for details. It is recommended to send
- this message if the
- <varname>$WATCHDOG_PID</varname>
- environment variable has been set to
- the PID of the service process, in
- every half the time interval that is
- specified in the
- <varname>$WATCHDOG_USEC</varname>
- environment variable. See
+ for information how to enable this
+ functionality and
<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- for details.</para></listitem>
+ for the details of how the service can
+ check if the the watchdog is enabled.
+ </para></listitem>
</varlistentry>
</variablelist>
diff --git a/man/sd_watchdog_enabled.xml b/man/sd_watchdog_enabled.xml
index 4164027640..462d7c6617 100644
--- a/man/sd_watchdog_enabled.xml
+++ b/man/sd_watchdog_enabled.xml
@@ -69,30 +69,37 @@
which the manager will act on the service if it did
not get such a notification.</para>
+ <para>If the <varname>$WATCHDOG_USEC</varname>
+ environment variable is set, and the
+ <varname>$WATCHDOG_PID</varname> variable is unset or
+ set to the PID of the current process, the service
+ manager expects notifications from this process. The
+ manager will usually terminate a service when it does
+ not get a notification message within the specified
+ time after startup and after each previous message. It
+ is recommended that a daemon sends a keep-alive
+ notification message to the service manager every half
+ of the time returned here. Notification messages may
+ be sent with
+ <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ with a message string of
+ <literal>WATCHDOG=1</literal>.</para>
+
<para>If the <parameter>unset_environment</parameter>
parameter is non-zero,
<function>sd_watchdog_enabled()</function> will unset
the <varname>$WATCHDOG_USEC</varname> and
<varname>$WATCHDOG_PID</varname> environment variables
- before returning (regardless of whether the function call
- itself succeeded or not). Further calls to
- <function>sd_watchdog_enabled()</function> will then
- return with zero, but the variable is no longer
- inherited by child processes.</para>
+ before returning (regardless of whether the function
+ call itself succeeded or not). Those variables are no
+ longer inherited by child processes. Further calls to
+ <function>sd_watchdog_enabled()</function> will also
+ return with zero.</para>
<para>If the <parameter>usec</parameter> parameter is
non-NULL, <function>sd_watchdog_enabled()</function>
- will return the timeout in µs for the watchdog
- logic. The service manager will usually terminate a
- service when it did not get a notification message
- within the specified time after startup and after each
- previous message. It is recommended that a daemon
- sends a keep-alive notification message to the service
- manager every half of the time returned
- here. Notification messages may be sent with
- <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- with a message string of
- <literal>WATCHDOG=1</literal>.</para>
+ will write the timeout in µs for the watchdog
+ logic to it.</para>
<para>To enable service supervision with the watchdog
logic, use <varname>WatchdogSec=</varname> in service
@@ -126,7 +133,6 @@
of the current process, under the assumption that in
that case, the variables were set for a different
process further up the process tree.</para>
-
</refsect1>
<refsect1>
@@ -157,6 +163,19 @@
</refsect1>
<refsect1>
+ <title>History</title>
+
+ <para>The watchdog functionality and the
+ <varname>$WATCHDOG_USEC</varname> variable were
+ added in systemd-41.</para>
+
+ <para><function>sd_watchdog_enabled()</function>
+ function was added in systemd-209. Since that version
+ the <varname>$WATCHDOG_PID</varname> variable is also
+ set.</para>
+ </refsect1>
+
+ <refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
diff --git a/src/libsystemd/sd-daemon/sd-daemon.c b/src/libsystemd/sd-daemon/sd-daemon.c
index 46241f77ff..1f2a53393f 100644
--- a/src/libsystemd/sd-daemon/sd-daemon.c
+++ b/src/libsystemd/sd-daemon/sd-daemon.c
@@ -491,39 +491,35 @@ _public_ int sd_booted(void) {
}
_public_ int sd_watchdog_enabled(int unset_environment, uint64_t *usec) {
- const char *e;
+ const char *s, *p = ""; /* p is set to dummy value to do unsetting */
uint64_t u;
- pid_t pid;
- int r;
+ int r = 0;
- e = getenv("WATCHDOG_PID");
- if (!e) {
- r = 0;
+ s = getenv("WATCHDOG_USEC");
+ if (!s)
goto finish;
- }
- r = parse_pid(e, &pid);
+ r = safe_atou64(s, &u);
if (r < 0)
goto finish;
-
- /* Is this for us? */
- if (getpid() != pid) {
- r = 0;
- goto finish;
- }
-
- e = getenv("WATCHDOG_USEC");
- if (!e) {
+ if (u <= 0) {
r = -EINVAL;
goto finish;
}
- r = safe_atou64(e, &u);
- if (r < 0)
- goto finish;
- if (u <= 0) {
- r = -EINVAL;
- goto finish;
+ p = getenv("WATCHDOG_PID");
+ if (p) {
+ pid_t pid;
+
+ r = parse_pid(p, &pid);
+ if (r < 0)
+ goto finish;
+
+ /* Is this for us? */
+ if (getpid() != pid) {
+ r = 0;
+ goto finish;
+ }
}
if (usec)
@@ -532,10 +528,10 @@ _public_ int sd_watchdog_enabled(int unset_environment, uint64_t *usec) {
r = 1;
finish:
- if (unset_environment) {
- unsetenv("WATCHDOG_PID");
+ if (unset_environment && s)
unsetenv("WATCHDOG_USEC");
- }
+ if (unset_environment && p)
+ unsetenv("WATCHDOG_PID");
return r;
}