Re: udevsynthesize as a udevstart+coldplug replacement

["Mika Penttilä" <mika.penttila@kolumbus.fi>]

Kay Sievers wrote:

>On Tue, Aug 23, 2005 at 10:46:43PM +0300, Mika Penttilä wrote:
>  
>
>>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
>>>      
>>>
>
>  
>
>>What if udevd receives netlink messages and goes into "ignore unix 
>>socket" mode before/while synthesize?
>>    
>>
>
>No such mode exists. :) Only events with a SEQNUM set will possibly be
>ignored if received from userspace after netlink activity is detected.
>
>Kay
>
>  
>
Ok, there's the (seqnum != 0 && netlink active) test which keeps these 
messages passing through.

Thanks,
Mika




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