Message-ID: <46434123.8040801@drzeus.cx>
Date: Thu, 10 May 2007 17:58:27 +0200
From: Pierre Ossman <drzeus@drzeus.cx>
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To: Haavard Skinnemoen <hskinnemoen@atmel.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] MMC: Flush mmc workqueue late in the boot sequence
References: <117879333788-git-send-email-hskinnemoen@atmel.com>	<46430A49.9090803@drzeus.cx>	<20070510143737.54969394@dhcp-252-105.norway.atmel.com>	<46432212.9070008@drzeus.cx> <20070510163348.0a117d92@dhcp-252-105.norway.atmel.com>
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Haavard Skinnemoen wrote:
>=20
> Ok, is there any better way to achieve the same this? As far as I
> can tell, mmc_remove_host() uses mmc_flush_scheduled_work() for the
> same purpose -- it ensures that scans that have already been started
> will have completed before the function continues.
>=20

Not quite. mmc_remove_host() doesn't care if a detect has been executed o=
r not,
it only cares about whether or not one is executing right now. So in orde=
r for
your patch to work, there must be no way that mmc_finish_detect() is call=
ed
before the detect is scheduled.

>=20
> I wouldn't call it luck. The way mmc_rescan() is implemented, any scans=

> that are started before late_initcall time are completed before
> mmc_finish_detect() returns. The steps are all done synchronously in
> the workqueue function.
>=20

Indeed. But it is not by design that they are scheduled before late_initc=
all().
Also, flushing the workqueue is also not a by-design way of completing a =
scan,
it just happens to be that way right now.

> And I never realized that using a block device as a parameter to the
> root=3D parameter could possibly be "unofficial" functionality...?

Then you've learned something new. ;)

Only some devices work that way (generally only those with "simple" inter=
faces).
And most things are these days behind more advanced buses, more akin to a=
 network.

Generally, not waiting for a lot of hardware is a good thing as it speeds=
 up
boot times. In my mind, the proper way is having a script in an initrd th=
at
waits for just the parts of the hardware that this particular system need=
s.
Everything else can be brought up in the background.

Rgds
Pierre


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