From 63c211803a272d59dcb11af82ad0364b3d1d2a2e Mon Sep 17 00:00:00 2001
From: Chuansheng Liu <chuansheng.liu@intel.com>
Date: Tue, 5 Nov 2013 14:52:45 +0800
Subject: [PATCH] mmc: sdhci: Setting the host->mrq to NULL before executing
 tuning

In function sdhci_request(), it is possible to do the tuning execution
like below:

sdhci_request() {
	spin_lock_irqsave(&host->lock, flags);
	host->mrq = mrq;
	...
	spin_unlock_irqrestore(&host->lock, flags);

<=== Here it is possible one pending finish_tasklet get running
     and it will operate the original mrq, and notified the mrq
     is done, and causes memory corruption.

	sdhci_execute_tuning(mmc, tuning_opcode);
	spin_lock_irqsave(&host->lock, flags);
	host->mrq = mrq;
...
}

In the above race place, the original mrq should not be finished wrongly,
so here before unlock the spinlock, we need to set the host->mrq to NULL
to avoid this case.

Signed-off-by: Liu, Chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
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