Re: udevsynthesize as a udevstart+coldplug replacement

["Alexander E. Patrakov" <patrakov@ums.usu.ru>]

Kay Sievers wrote:

>Here is "udevsynthesize" a possible replacement for the udevstart/coldplug
>combination we currently have. Usually very early in the boot process, it
>gets all available devices from sysfs and synthesizes the events these
>devices would have generated at creation time.
>The events are directly passed to the udevd daemom socket. udevd does all the
>work and runs all the events asynchronously. udevsynthesize itself does
>not read any udev rule.
>
>It scans block and class devices to create the the device nodes for already
>available devices, which obsoletes the run of udevstart.
>After that, it scans for bus devices, which events may load modules or
>configure the device. If the bus type is known, the usual bus-specific
>values are added to the event environment.
>
>With the "rules-in-daemon" patch, the whole udevstart/coldplug handling
>(700 events) takes less than a second CPU time on a 1.7Ghz laptop.
>
>A typical boot script would do:
>  prepare tmpfs on /dev
>  create /dev/null
>  start /sbin/udevd
>  disable /proc/sys/kernel/hotplug (the input layer is still broken and needs a kernel patch)
>  run /sbin/udevsynthesize
>
>Have fun,
>Kay
>  
>

Could you please tell where to add swap activation and ext2 filesystem 
checks in this scenario to make sure that there's no race between udev 
(that creates the device asynchronously, as you said) and swapon/fsck 
(that may want to use the device)?

-- 
Alexander E. Patrakov


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