linux-kernel - [PATCH] mmc: sdhci: don't read cd-gpio while holding spinlock

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Message-Id: <1395341232-14490-1-git-send-email-abrestic@chromium.org>
Date:	Thu, 20 Mar 2014 11:47:12 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Chris Ball <chris@...ntf.net>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...omium.org>
Subject: [PATCH] mmc: sdhci: don't read cd-gpio while holding spinlock

mmc_request() reads the cd-gpio via mmc_gpio_get_cd(), which can sleep,
while holding host->lock.  This may result in the following BUG:

  BUG: spinlock wrong CPU on CPU#2, kworker/u8:16/4296
  lock: 0xea6b9c80, .magic: dead4ead, .owner: kworker/u8:16/4296, .owner_cpu: 0
  CPU: 2 PID: 4296 Comm: kworker/u8:16 Tainted: G         C   3.10.18 #137
  Workqueue: kmmcd mmc_rescan
  [<8020cf8c>] (unwind_backtrace+0x0/0x118) from [<8020a0c8>] (show_stack+0x20/0x24)
  [<8020a0c8>] (show_stack+0x20/0x24) from [<8075e5b8>] (dump_stack+0x20/0x28)
  [<8075e5b8>] (dump_stack+0x20/0x28) from [<804184a8>] (spin_dump+0x80/0x94)
  [<804184a8>] (spin_dump+0x80/0x94) from [<804184e8>] (spin_bug+0x2c/0x30)
  [<804184e8>] (spin_bug+0x2c/0x30) from [<80418790>] (do_raw_spin_unlock+0x94/0xd4)
  [<80418790>] (do_raw_spin_unlock+0x94/0xd4) from [<80761a44>] (_raw_spin_unlock_irqrestore+0x1c/0x24)
  [<80761a44>] (_raw_spin_unlock_irqrestore+0x1c/0x24) from [<805ff66c>] (sdhci_request+0x1c8/0x1d0)
  [<805ff66c>] (sdhci_request+0x1c8/0x1d0) from [<805ebb5c>] (mmc_start_request+0xec/0xf4)
  [<805ebb5c>] (mmc_start_request+0xec/0xf4) from [<805ebcbc>] (mmc_wait_for_req+0x80/0xf4)
  ...

Read the cd-gpio before acquiring the spinlock instead.

Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
---
 drivers/mmc/host/sdhci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 04a5e25..f2ef978 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1340,6 +1340,7 @@ static void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	u32 tuning_opcode;
 
 	host = mmc_priv(mmc);
+	present = mmc_gpio_get_cd(host->mmc);
 
 	sdhci_runtime_pm_get(host);
 
@@ -1371,7 +1372,6 @@ static void sdhci_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	 *     zero: cd-gpio is used, and card is removed
 	 *     one: cd-gpio is used, and card is present
 	 */
-	present = mmc_gpio_get_cd(host->mmc);
 	if (present < 0) {
 		/* If polling, assume that the card is always present. */
 		if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION)
-- 
1.9.0.279.gdc9e3eb

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