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udevd: add support for S6/dinit-compatible readiness notification #290

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udevd: add support for S6/dinit-compatible readiness notification #290

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7 changes: 6 additions & 1 deletion man/udevd.8
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ udevd \- Device event managing daemon
.PP
udevd
.HP \w'\fB/sbin/udevd\fR\ 'u
\fB/sbin/udevd\fR [\fB\-\-daemon\fR] [\fB\-\-debug\fR] [\fB\-\-children\-max=\fR] [\fB\-\-exec\-delay=\fR] [\fB\-\-event\-timeout=\fR] [\fB\-\-resolve\-names=early|late|never\fR] [\fB\-\-version\fR] [\fB\-\-help\fR]
\fB/sbin/udevd\fR [\fB\-\-daemon\fR] [\fB\-\-debug\fR] [\fB\-\-ready\-notify=\fR] [\fB\-\-children\-max=\fR] [\fB\-\-exec\-delay=\fR] [\fB\-\-event\-timeout=\fR] [\fB\-\-resolve\-names=early|late|never\fR] [\fB\-\-version\fR] [\fB\-\-help\fR]
.SH "DESCRIPTION"
.PP
\fBudevd\fR
Expand All @@ -47,6 +47,11 @@ Detach and run in the background\&.
Print debug messages to standard error\&.
.RE
.PP
\fB\-r\fR, \fB\-\-ready\-notify=\fR
.RS 4
Issue (S6/dinit compatible) readiness notification via a file descriptor\&. A short message followed by a newline character will be sent via the specified file descriptor (inherited from the parent process) when initialization is complete\&.
.RE
.PP
\fB\-c\fR, \fB\-\-children\-max=\fR
.RS 4
Limit the number of events executed in parallel\&.
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11 changes: 11 additions & 0 deletions man/udevd.xml
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Expand Up @@ -34,6 +34,7 @@
<command>/sbin/udevd</command>
<arg><option>--daemon</option></arg>
<arg><option>--debug</option></arg>
<arg><option>--ready-notify=</option></arg>
<arg><option>--children-max=</option></arg>
<arg><option>--exec-delay=</option></arg>
<arg><option>--event-timeout=</option></arg>
Expand Down Expand Up @@ -75,6 +76,16 @@
</listitem>
</varlistentry>

<varlistentry>
<term><option>-r</option>, <option>--ready-notify=</option></term>
<listitem>
<para>Issue (S6/dinit compatible) readiness notification via a
file descriptor. A short message followed by a newline character
will be sent via the specified file descriptor (inherited from
the parent process) when initialization is complete.</para>
</listitem>
</varlistentry>

<varlistentry>
<term><option>-c</option>, <option>--children-max=</option></term>
<listitem>
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23 changes: 23 additions & 0 deletions src/udev/udevd.c
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Expand Up @@ -62,6 +62,7 @@ static int worker_watch[2] = { -1, -1 };
static int fd_signal = -1;
static int fd_ep = -1;
static int fd_inotify = -1;
static int fd_ready = -1;
static bool stop_exec_queue;
static bool reload;
static bool arg_debug = false;
Expand All @@ -76,6 +77,7 @@ static UDEV_LIST(event_list);
Hashmap *workers;
static struct udev_list properties_list;
static bool udev_exit;
static char udevd_ready_string[] = "udevd ready\n";

enum event_state {
EVENT_UNDEF,
Expand Down Expand Up @@ -1036,6 +1038,7 @@ static void help(void) {
" -V --version Print version of the program\n"
" -d --daemon Detach and run in the background\n"
" -D --debug Enable debug output\n"
" -r --ready-notify=FD Notify readiness via file descriptor\n"
" -c --children-max=INT Set maximum number of workers\n"
" -e --exec-delay=SECONDS Seconds to wait before executing RUN=\n"
" -t --event-timeout=SECONDS Seconds to wait before terminating an event\n"
Expand All @@ -1048,6 +1051,7 @@ static int parse_argv(int argc, char *argv[]) {
static const struct option options[] = {
{ "daemon", no_argument, NULL, 'd' },
{ "debug", no_argument, NULL, 'D' },
{ "ready-notify", required_argument, NULL, 'r' },
{ "children-max", required_argument, NULL, 'c' },
{ "exec-delay", required_argument, NULL, 'e' },
{ "event-timeout", required_argument, NULL, 't' },
Expand Down Expand Up @@ -1104,6 +1108,11 @@ static int parse_argv(int argc, char *argv[]) {
return 0;
}
break;
case 'r':
r = safe_atou(optarg, &fd_ready);
if (r < 0)
log_warning("Invalid --ready-notify ignored: %s", optarg);
break;
case 'h':
help();
return 0;
Expand Down Expand Up @@ -1372,6 +1381,20 @@ int main(int argc, char *argv[]) {
goto exit;
}

if (fd_ready != -1) {
size_t to_write = sizeof(udevd_ready_string) - 1;
char *wptr = udevd_ready_string;
do {
int r = write(fd_ready, wptr, to_write);
if (r < 0) {
log_error_errno(errno, "failed to write to readiness fd: %m");
break;
}
to_write -= r;
wptr += r;
} while (to_write > 0);
}

for (;;) {
static usec_t last_usec;
struct epoll_event ev[8];
Expand Down