linux-kernel - [PATCH] mmc: rtsx: fix possible circular locking dependency

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Message-ID: <1397612325-4968-1-git-send-email-micky_ching@realsil.com.cn>
Date:	Wed, 16 Apr 2014 09:38:44 +0800
From:	<micky_ching@...lsil.com.cn>
To:	<chris@...ntf.net>, <sameo@...ux.intel.com>
CC:	<gregkh@...uxfoundation.org>, <dan.carpenter@...cle.com>,
	<ulf.hansson@...aro.org>, <devel@...uxdriverproject.org>,
	<linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
	<rogerable@...ltek.com>, <wei_wang@...lsil.com.cn>,
	Micky Ching <micky_ching@...lsil.com.cn>
Subject: [PATCH] mmc: rtsx: fix possible circular locking dependency

From: Micky Ching <micky_ching@...lsil.com.cn>

To avoid dead lock, we need make sure host->lock is always acquire
before pcr->lock. But in irq handler, we acquired pcr->lock in rtsx mfd
driver, and sd_isr_done_transfer() is called during pcr->lock already
acquired. Since in sd_isr_done_transfer() the only work we do is schdule
tasklet, the cmd_tasklet and data_tasklet never conflict, so it is safe
to remove spin_lock() here.

Signed-off-by: Micky Ching <micky_ching@...lsil.com.cn>
---
 drivers/mmc/host/rtsx_pci_sdmmc.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/mmc/host/rtsx_pci_sdmmc.c b/drivers/mmc/host/rtsx_pci_sdmmc.c
index 453e1d4..40695e0 100644
--- a/drivers/mmc/host/rtsx_pci_sdmmc.c
+++ b/drivers/mmc/host/rtsx_pci_sdmmc.c
@@ -108,12 +108,10 @@ static void sd_isr_done_transfer(struct platform_device *pdev)
 {
 	struct realtek_pci_sdmmc *host = platform_get_drvdata(pdev);
 
-	spin_lock(&host->lock);
 	if (host->cmd)
 		tasklet_schedule(&host->cmd_tasklet);
-	if (host->data)
+	else if (host->data)
 		tasklet_schedule(&host->data_tasklet);
-	spin_unlock(&host->lock);
 }
 
 static void sd_request_timeout(unsigned long host_addr)
-- 
1.7.9.5

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