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From: Ohad Ben-Cohen <ohad@wizery.com>
Date: Sun, 26 Dec 2010 16:53:57 +0200
Message-ID: <AANLkTinvBD6NhHY7PMw9NSJNBW77-Gah8Vcow6t1aiCT@mail.gmail.com>
Subject: Re: [linux-pm] subtle pm_runtime_put_sync race and sdio functions
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	linux-pm@lists.linux-foundation.org,
	Johannes Berg <johannes@sipsolutions.net>,
	linux-wireless@vger.kernel.org, linux-mmc@vger.kernel.org,
	Ido Yariv <ido@wizery.com>,
	Kevin Hilman <khilman@deeprootsystems.com>
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Sender: linux-wireless-owner@vger.kernel.org

On Sun, Dec 26, 2010 at 1:45 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> (It still is not a race, though.)

Thread 1
=======

suspend_handler_of_a_random_device()
{
    return failure;
}

Thread 2
=======

suspend_handler_of_our_mmc_host_controller()
{
    invoke our sdio suspend handler and power down the card (directly);
    return success;
}

If thread 2 wins => everything is cool
If thread 1 wins => our driver will not be able to resume

The race begins after mac80211 invokes our driver's power off handler,
which is using pm_runtime_put_sync().