linux-kernel - Re: Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD card is inserted]

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Date:	Mon, 25 Feb 2008 15:00:51 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pierre Ossman <drzeus-mmc@...eus.cx>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	David Brownell <david-b@...bell.net>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD card
 is inserted]

On Mon, 25 Feb 2008, Pierre Ossman wrote:

> > What do you think of the patch attached to comment #40 in the Bugzilla 
> > entry?
> > 
> 
> Looks ok. As long as those two synchronization points are guaranteed,
> then I'm happy.

Maybe a better approach would be to leave the workqueue unfreezable,
and keep cancel_delayed_work_sync() in mmc_suspend_host().  It would
then be necessary to add a test to verify, if there is a card attached,
that the card is indeed suspended.  After all, it's possible that the
cancel_delayed_work_sync() ended up waiting for a job already running
on the workqueue to register a new card!  (The same would be true even 
with flush_scheduled_work.)

Also, as a bit of defensive programming, it might be a good idea to add
a "suspended" flag to the mmc_host structure.  If mmc_rescan() sees
that the flag is set then it should return immediately.  This would
protect against host drivers that aren't careful to disable detect
IRQs before calling mmc_suspend_host().

Alan Stern

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