package/eudev: tweak initscript

Make the udev initscript trigger in a coherent way, i.e. first set subsystems, then device and then let the whole thing settle. Otherwise for usb_modeswitch udev rules they never kick in since the storage aspect (device) gets claimed first and the switch ignored.

Signed-off-by Gustavo Zacarias <[email protected]>

---
 package/eudev/S10udev | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

package/eudev/S10udev +0 -0

index 107dfd5..c3eafce 100755

package/eudev/S10udev +0 -0

         echo "done"
         ;;
     stop)

Signature · 6 lines

2.0.4

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Hmmm... This exit won't do much: it exits a sub-shell, so the initscript will still continue...

package/eudev/S10udev case "$1" in · line 35

Quoted 5 lines

package/eudev/S10udev +3 -2

-        udevadm trigger --action=add
-        udevadm settle
+        udevadm trigger --type=subsystems --action=add
+        udevadm trigger --type=devices --action=add
+        udevadm settle --timeout=10

Why did you add a timeout, and not explain it?

Also, are 10 seconds really enough? What happens if a device takes longer than 10s to initialise (and it is needed to boot, like a slow USB mass-storage) ?

Quoted 3 lines

Hmmm... This exit won't do much: it exits a sub-shell, so the initscript will still continue...

I've focused on fixing the one problem, i didn't audit the whole script.

Quoted 6 lines

Quoted 5 lines

package/eudev/S10udev +3 -2

-        udevadm trigger --action=add
-        udevadm settle
+        udevadm trigger --type=subsystems --action=add
+        udevadm trigger --type=devices --action=add
+        udevadm settle --timeout=10

Quoted 5 lines

Why did you add a timeout, and not explain it?

Also, are 10 seconds really enough? What happens if a device takes longer than 10s to initialise (and it is needed to boot, like a slow USB mass-storage) ?

It just seems prudent to avoid a stall, but yeah forgot to mention it, it's the usual practice in many distros.

You've got rootwait & friends for that, remember this is post mount-root so it doesn't matter there.

And if you're doing initramfs then
switching/pivoting to some other root, well, you're scripting it, you should take care of it there since you're doing the mount.

Mine has no timeout, but from man udevadm, the default is 120s:

udevadm settle [options]
Watches the udev event queue, and exits if all current events are handled.

--timeout=seconds
Maximum number of seconds to wait for the event queue to become empty. The default value is 120 seconds. A value of 0 will check if the queue is empty and always return immediately.

So, I think 10s are a bit too short, but can not really suggest a better default. Maybe we could just keep the default timeout, even though it is a bit long?

Whether we wait 10 or 120 seconds, if something's stuck, there's not much we can do about it. My distro, however, does this:

    # wait for the udevd childs to finish
    log_action_begin_msg "Waiting for /dev to be fully populated"
    if udevadm settle; then
        log_action_end_msg 0
    else
        log_action_end_msg 0 'timeout'
    fi

Which we could actually do (except in a simpler way, like log the issue).

Not only USB mass-storage for root, but eth over USB, too. I've seen a USB bus take about 8s to properly initialise and enumerate all the devices, and a few seconds more for the USB-eth device to show up, and there was an NFS resource to be mounted from /etc/fstab.

Anyway, this is a corner case.