On 16 May 2011, Kay Sievers outgrape: > With devtmpfs you get the "early" /dev for free, and you preserve the > "early" /dev in the real root. Instead of mounting a 'tmpfs' just > mount a 'devtmpfs' at /dev, and it will be magically filled already, > that's the only difference. > > When mounting the real root, just mount --move it over to the real > root before switching to the real root. I'll have to see what busybox's switch_root does. I know it deletes the entire contents of the root directory it switches away from: I'll have to make sure that doesn't somehow include moved-away mountpoints. (I doubt it does.) > Maybe you can run: > udevadm monitor > in the background writing to a file, and get timestamps of your commands too. They're fine. After a bunch of straces, I think the problem is different. As I suspected from its intermittent nature, it's a race. When udevd starts up, it looks for an old database and converts it into a new-style /run database. This takes nonzero time, and is done *after* daemonization. Unfortunately, in the same time window it is quite possible to fit a pair of 'udevadm trigger's and a 'udevadm settle': and when udevadm settle kicks up and finds that udev hasn't even initialized yet, what does it do? Well, unless I misread the code udev_queue_get_queue_is_empty() returns 1 in this situation, so 'udevadm settle' returns EXIT_SUCCESS, and boom. My evidence for this is very thin: it's no more than a hypothesis really. My only evidence for this so far is that I haven't managed to get the failure to happen unless I mkdir the old udev directories first to force udev to do an old->new db conversion. It would be nice to gather more data, but it's hard to do that without perturbing the race :/ even an ls of /run slows it down enough that it doesn't happen anymore. Hm, perhaps an echo would be fast enough, it's a shell builtin after all... If I'm right (and I'm not sure I am, but it feels plausible), then I suspect the only fix is to move the db conversion so that it happens before daemonization. -- NULL && (void) -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
