linux-kernel - Re: asynchronous calls an the lack of --wait-for-completion options (e.g. modprobe, losetup, cryptsetup)

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Date:	Sat, 20 Jun 2009 21:20:11 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	Alexander Holler <holler@...oftware.de>,
	linux-kernel@...r.kernel.org
Subject: Re: asynchronous calls an the lack of --wait-for-completion options 
	(e.g. modprobe, losetup, cryptsetup)

On Fri, Jun 19, 2009 at 02:52, Robert Hancock<hancockrwd@...il.com> wrote:
> On 06/17/2009 07:39 AM, Alexander Holler wrote:

>> The problem is that when I'm e.g. calling modprobe loop, loop might not
>> has finished it's initialization, when modprobe returns.
>
> It will have. Just that udev won't have received the events and created the
> device node yet. So the solution would likely be on the udev side..

The brutal method to do this is to call:
  udevadm settle
after loading the module. It will block until all currently pending
events for udev are fully handled.

Recent udevadm versions also have a:
  --exit-if-exists=<filename>
option, which will make "settle" stop waiting if a given file exists.

Kay
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