linux-kernel - [109/200] ARM: 6146/1: sa1111: Prevent deadlock in resume path

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Message-Id: <20100701174255.628427493@clark.site>
Date:	Thu, 01 Jul 2010 10:43:19 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Marek Vasut <marek.vasut@...il.com>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: [109/200] ARM: 6146/1: sa1111: Prevent deadlock in resume path

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: =?UTF-8?q?Marek=20Va=C5=A1ut?= <marek.vasut@...il.com>

commit 3defb2476166445982a90c12d33f8947e75476c4 upstream.

This patch reorganises the sa1111_resume() function in a manner the spinlock
happens after calling the sa1111_wake(). This fixes two bugs:

1) This function called sa1111_wake() which tried to claim the same spinlock
   the sa1111_resume() already claimed. This would result in certain deadlock.

   Original idea for this part: Russell King <rmk+kernel@....linux.org.uk>

2) The function didn't unlock the spinlock in case the chip didn't report
   correct ID.

   Original idea for this part: Julia Lawall <julia@...u.dk>

Signed-off-by: Marek Vasut <marek.vasut@...il.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/arm/common/sa1111.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/arm/common/sa1111.c
+++ b/arch/arm/common/sa1111.c
@@ -951,8 +951,6 @@ static int sa1111_resume(struct platform
 	if (!save)
 		return 0;
 
-	spin_lock_irqsave(&sachip->lock, flags);
-
 	/*
 	 * Ensure that the SA1111 is still here.
 	 * FIXME: shouldn't do this here.
@@ -969,6 +967,13 @@ static int sa1111_resume(struct platform
 	 * First of all, wake up the chip.
 	 */
 	sa1111_wake(sachip);
+
+	/*
+	 * Only lock for write ops. Also, sa1111_wake must be called with
+	 * released spinlock!
+	 */
+	spin_lock_irqsave(&sachip->lock, flags);
+
 	sa1111_writel(0, sachip->base + SA1111_INTC + SA1111_INTEN0);
 	sa1111_writel(0, sachip->base + SA1111_INTC + SA1111_INTEN1);
 


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