[PATCH] Give a hint when 'udevd' is ready to operate

[PATCH] Give a hint when 'udevd' is ready to operate

[Enrico Scholz]

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Hello,

please apply the attached patch. It creates the '/dev/.udev' directory
when 'udevd' is ready to operate.

This helps init methods like 'initng' or 'minit' to stop future
processing (e.g. invoking 'udevtrigger') until 'udevd' is fully
initialized. Currently, there does not seem to exist a way to wait
for 'udevd' (resp. to check whether it is ready) and issued uevent's
may disappear silently.

With this patch, the init methods can test for /dev/.udev (e.g. waiting
actively or using inotify) after 'udevd' has been started.



Enrico

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--- udev-091/udevd.c.startup	2006-04-25 22:39:59.000000000 +0200
+++ udev-091/udevd.c	2006-04-28 10:00:48.000000000 +0200
@@ -946,6 +946,8 @@
 	chdir("/");
 	umask(022);
 
+	create_path(UDEV_ROOT);
+  
 	/* become session leader */
 	sid = setsid();
 	dbg("our session is %d", sid);

Re: [PATCH] Give a hint when 'udevd' is ready to operate

[Scott James Remnant]

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On Sat, 2006-04-29 at 11:08 +0200, Enrico Scholz wrote:

> please apply the attached patch. It creates the '/dev/.udev' directory
> when 'udevd' is ready to operate.
> 
This isn't needed.

Start udevd with the --daemon argument, it won't go into the background
until it's ready to process events.

So the following code works:

	udevd --daemon
	udevtrigger

Scott
-- 
Scott James Remnant
scott@ubuntu.com

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Re: [PATCH] Give a hint when 'udevd' is ready to operate

[Kay Sievers]

On Sat, Apr 29, 2006 at 01:46:20PM +0100, Scott James Remnant wrote:
> On Sat, 2006-04-29 at 11:08 +0200, Enrico Scholz wrote:
> 
> > please apply the attached patch. It creates the '/dev/.udev' directory
> > when 'udevd' is ready to operate.
> > 
> This isn't needed.
> 
> Start udevd with the --daemon argument, it won't go into the background
> until it's ready to process events.
> 
> So the following code works:
> 
> 	udevd --daemon
> 	udevtrigger

Yeah, that is the usual way and udevd makes sure not to return before
it's fully initialized. Waiting for a file from a daemon, just because
the minit-like stuff tries to be smart (daemons don't detach) sounds
weird. Anyway, the current udevd exports the seqnum of the kernel, so
one can wait for that, even when it's a silly workaround a problem that
does not exist in reality.

Kay


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Re: [PATCH] Give a hint when 'udevd' is ready to operate

[Enrico Scholz]

Scott James Remnant <scott@ubuntu.com> writes:

>> please apply the attached patch. It creates the '/dev/.udev' directory
>> when 'udevd' is ready to operate.
>> 
> This isn't needed.
>
> Start udevd with the --daemon argument,

Does not work nice with modern init methods like 'initng' and 'minit'
because they want to avoid forking daemons. Keeping track of the status
of daemons (e.g. needed for the 'respawn' or 'send-signal-to-daemon'
feature) is more difficultly when daemon goes into background.



Enrico



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Re: [PATCH] Give a hint when 'udevd' is ready to operate

[Enrico Scholz]

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Kay Sievers <kay.sievers@vrfy.org> writes:

>> 	udevd --daemon
>> 	udevtrigger
>
> Yeah, that is the usual way and udevd makes sure not to return before
> it's fully initialized. Waiting for a file from a daemon, just because
> the minit-like stuff tries to be smart (daemons don't detach) sounds
> weird. Anyway, the current udevd exports the seqnum of the kernel, so
> one can wait for that,

Does not work; the first call to export_initial_seqnum() (before fork())
is a noop because

|        strlcpy(filename, udev_root, sizeof(filename));
|        strlcat(filename, "/" EVENT_SEQNUM, sizeof(filename));
|        fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0644);

fails due to the non-existing '/dev/.udev' path. So, my patch should be
applied earlier


|         udev_rules_init(&rules, 1);
|
| +       create_path(udev_root);
|         export_initial_seqnum();
|
|         if (daemonize) {



Enrico

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Re: [PATCH] Give a hint when 'udevd' is ready to operate

[David Gómez]

Hi Enrico,

On Apr 29 at 03:12:39, Enrico Scholz wrote:
> Does not work nice with modern init methods like 'initng' and 'minit'
> because they want to avoid forking daemons.

I think that "modern" approach it's not the right one. It shouldn't
be the init process the supervisor of the daemons launched at the
boot time... 

cheers,

-- 
David Gómez                                      Jabber ID: davidge@jabber.org


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Re: [PATCH] Give a hint when 'udevd' is ready to operate

[Kay Sievers]

On Sat, Apr 29, 2006 at 04:11:34PM +0200, Enrico Scholz wrote:
> Kay Sievers <kay.sievers@vrfy.org> writes:
> 
> >> 	udevd --daemon
> >> 	udevtrigger
> >
> > Yeah, that is the usual way and udevd makes sure not to return before
> > it's fully initialized. Waiting for a file from a daemon, just because
> > the minit-like stuff tries to be smart (daemons don't detach) sounds
> > weird. Anyway, the current udevd exports the seqnum of the kernel, so
> > one can wait for that,
> 
> Does not work; the first call to export_initial_seqnum() (before fork())
> is a noop because
> 
> |        strlcpy(filename, udev_root, sizeof(filename));
> |        strlcat(filename, "/" EVENT_SEQNUM, sizeof(filename));
> |        fd = open(filename, O_WRONLY|O_TRUNC|O_CREAT, 0644);
> 
> fails due to the non-existing '/dev/.udev' path. So, my patch should be
> applied earlier

Just create that directory yourself and wait for the seqnum file to
appear. In the devel tree it's already changed 3 days ago, but not in
a released version.

Kay


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