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login: add sd_login_monitor_get_timeout() public api call

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We don't need this right now, but we should keep our options open, in
case we need more than just an fd for waking up.
This commit is contained in:
Lennart Poettering 2013-04-04 18:31:22 +02:00
parent 60491a2869
commit 667c24a6a8
5 changed files with 92 additions and 11 deletions
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61
man/sd_login_monitor_new.xml
View File

@ -48,6 +48,7 @@
<refname>sd_login_monitor_flush</refname>
<refname>sd_login_monitor_get_fd</refname>
<refname>sd_login_monitor_get_events</refname>
<refname>sd_login_monitor_get_timeout</refname>
<refname>sd_login_monitor</refname>
<refpurpose>Monitor login sessions, seats and users</refpurpose>
</refnamediv>
@ -82,6 +83,12 @@
<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_login_monitor_get_timeout</function></funcdef>
<paramdef>sd_login_monitor* <parameter>m</parameter></paramdef>
<paramdef>uint64_t* <parameter>timeout_usec</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
@ -130,7 +137,9 @@
or a similar interface. The application should include
the returned file descriptor as wake-up source for the
events mask returned by
<function>sd_login_monitor_get_events()</function>. Whenever
<function>sd_login_monitor_get_events()</function>. It
should pass a timeout value as returned by
<function>sd_login_monitor_get_timeout()</function>. Whenever
a wake-up is triggered the file descriptor needs to be
reset via
<function>sd_login_monitor_flush()</function>. An
@ -146,15 +155,51 @@
and similar to fill into the
<literal>.events</literal> field of <literal>struct
pollfd</literal>.</para>
<para><function>sd_login_monitor_get_timeout()</function>
will return a timeout value for usage in
<function>poll()</function>. This returns a value in
microseconds since the epoch of CLOCK_MONOTONIC for
timing out <function>poll()</function> in
<literal>timeout_usec</literal>. See
<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for details about
<literal>CLOCK_MONOTONIC</literal>. If there's no
timeout to wait for this will fill in
<literal>(uint64_t) -1</literal> instead. Note that
<function>poll()</function> takes a relative timeout
in milliseconds rather than an absolute timeout in
microseconds. To convert the absolute 'us' timeout into
relative 'ms', use code like the following:</para>
<programlisting>uint64_t t;
int msec;
sd_login_monitor_get_timeout(m, &amp;t);
if (t == (uint64_t) -1)
msec = -1;
else {
struct timespec ts;
uint64_t n;
clock_getttime(CLOCK_MONOTONIC, &amp;ts);
n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
}</programlisting>
<para>The code above does not do any error checking
for brevity's sake. The calculated <literal>msec</literal>
integer can be passed directly as
<function>poll()</function>'s timeout
parameter.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success
<function>sd_login_monitor_new()</function> and
<function>sd_login_monitor_flush()</function> return 0
or a positive integer. On success
<function>sd_login_monitor_new()</function>,
<function>sd_login_monitor_flush()</function> and
<function>sd_login_monitor_get_timeout()</function>
return 0 or a positive integer. On success
<function>sd_login_monitor_get_fd()</function> returns
a Unix file descriptor. On success
<function>sd_login_monitor_get_events()</function>
@ -173,8 +218,9 @@
<para>The <function>sd_login_monitor_new()</function>,
<function>sd_login_monitor_unref()</function>,
<function>sd_login_monitor_flush()</function>,
<function>sd_login_monitor_get_fd()</function> and
<function>sd_login_monitor_get_events()</function>
<function>sd_login_monitor_get_fd()</function>,
<function>sd_login_monitor_get_events()</function> and
<function>sd_login_monitor_get_timeout()</function>
interfaces are available as shared library, which can
be compiled and linked to with the
<literal>libsystemd-login</literal>
@ -189,7 +235,8 @@
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_get_seats</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>
<citerefentry><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
<citerefentry><refentrytitle>clock_gettime</refentrytitle><manvolnum>2</manvolnum></citerefentry>
</para>
</refsect1>

1
src/login/libsystemd-login.sym
View File

@ -62,4 +62,5 @@ global:
LIBSYSTEMD_LOGIN_201 {
global:
sd_login_monitor_get_events;
sd_login_monitor_get_timeout;
} LIBSYSTEMD_LOGIN_198;

18
src/login/sd-login.c
View File

@ -804,5 +804,23 @@ _public_ int sd_login_monitor_get_events(sd_login_monitor *m) {
if (!m)
return -EINVAL;
/* For now we will only return POLLIN here, since we don't
* need anything else ever for inotify. However, let's have
* this API to keep our options open should we later on need
* it. */
return POLLIN;
}
_public_ int sd_login_monitor_get_timeout(sd_login_monitor *m, uint64_t *timeout_usec) {
if (!m)
return -EINVAL;
if (!timeout_usec)
return -EINVAL;
/* For now we will only return (uint64_t) -1, since we don't
* need any timeout. However, let's have this API to keep our
* options open should we later on need it. */
*timeout_usec = (uint64_t) -1;
return 0;
}

19
src/login/test-login.c
View File

@ -183,12 +183,23 @@ int main(int argc, char* argv[]) {
r = sd_login_monitor_new("session", &m);
assert_se(r >= 0);
zero(pollfd);
pollfd.fd = sd_login_monitor_get_fd(m);
pollfd.events = sd_login_monitor_get_events(m);
for (n = 0; n < 5; n++) {
r = poll(&pollfd, 1, -1);
usec_t timeout, nw;
zero(pollfd);
assert_se((pollfd.fd = sd_login_monitor_get_fd(m)) >= 0);
assert_se((pollfd.events = sd_login_monitor_get_events(m)) >= 0);
assert_se(sd_login_monitor_get_timeout(m, &timeout) >= 0);
nw = now(CLOCK_MONOTONIC);
r = poll(&pollfd, 1,
timeout == (uint64_t) -1 ? -1 :
timeout > nw ? (int) ((timeout - nw) / 1000) :
0);
assert_se(r >= 0);
sd_login_monitor_flush(m);

4
src/systemd/sd-login.h
View File

@ -23,6 +23,7 @@
***/
#include <sys/types.h>
#include <inttypes.h>
#ifdef __cplusplus
extern "C" {
@ -159,6 +160,9 @@ int sd_login_monitor_get_fd(sd_login_monitor *m);
/* Get poll() mask to monitor */
int sd_login_monitor_get_events(sd_login_monitor *m);
/* Get timeout for poll(), as usec value relative to CLOCK_MONOTONIC's epoch */
int sd_login_monitor_get_timeout(sd_login_monitor *m, uint64_t *timeout_usec);
#ifdef __cplusplus
}
#endif