| Message ID | 1413827120-11083-1-git-send-email-gustavo@zacarias.com.ar |
|---|---|
| State | Superseded |
| Headers | show |
Gustavo, All, On 2014-10-20 14:45 -0300, Gustavo Zacarias spake thusly: > 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 <gustavo@zacarias.com.ar> > --- > package/eudev/S10udev | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/package/eudev/S10udev b/package/eudev/S10udev > index 107dfd5..c3eafce 100755 > --- a/package/eudev/S10udev > +++ b/package/eudev/S10udev > @@ -30,8 +30,9 @@ case "$1" in > printf "Populating ${udev_root:-/dev} using udev: " > printf '\000\000\000\000' > /proc/sys/kernel/hotplug > $UDEV_BIN -d || (echo "FAIL" && exit 1) Hmmm... This exit won't do much: it exits a sub-shell, so the initscript will still continue... > - 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) ? Regards, Yann E. MORIN. > echo "done" > ;; > stop) > -- > 2.0.4 > > _______________________________________________ > buildroot mailing list > buildroot@busybox.net > http://lists.busybox.net/mailman/listinfo/buildroot
On 10/20/2014 02:54 PM, Yann E. MORIN wrote: > 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. >> - 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) ? 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. Regards.
Gustavo, All, On 2014-10-20 14:57 -0300, Gustavo Zacarias spake thusly: > On 10/20/2014 02:54 PM, Yann E. MORIN wrote: > > > 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. Sorry, that was not a critcism of your patch. I just noticed it by chance... > >> - 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) ? > > It just seems prudent to avoid a stall, but yeah forgot to mention it, > it's the usual practice in many distros. 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). > You've got rootwait & friends for that, remember this is post mount-root > so it doesn't matter there. 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. Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Regards, Yann E. MORIN. > 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.
On 10/20/2014 03:10 PM, Yann E. MORIN wrote: > 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? 120s sounds brutal IMHO, you'll have to wait 2 full minutes to see anything. But yeah we could argue 10s is a bit short, maybe 30s is a good compromise? > 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). Probably something like... udevadm settle --timeout=30 || echo "udevadm settle timed out!" > 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. One would hope you don't switch root to nfs until you get the proper mount too which would mean a valid ip address as well (this without using the kernel nfsroot/dhcp client). Using the kernel subsystem i never tried using ethernet over usb but presumably rootwait would wait until ip negotiation is done? (again dunno what happens with the internal dhcp client if eth* isn't ready yet). Regards.
diff --git a/package/eudev/S10udev b/package/eudev/S10udev index 107dfd5..c3eafce 100755 --- a/package/eudev/S10udev +++ b/package/eudev/S10udev @@ -30,8 +30,9 @@ case "$1" in printf "Populating ${udev_root:-/dev} using udev: " printf '\000\000\000\000' > /proc/sys/kernel/hotplug $UDEV_BIN -d || (echo "FAIL" && exit 1) - udevadm trigger --action=add - udevadm settle + udevadm trigger --type=subsystems --action=add + udevadm trigger --type=devices --action=add + udevadm settle --timeout=10 echo "done" ;; stop)
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 <gustavo@zacarias.com.ar> --- package/eudev/S10udev | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)