linux-kernel - [RFC PATCH] spi/bcm63xx: Ensure that memory is freed only after it is no longer used

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Date:	Fri, 10 Aug 2012 13:56:27 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	spi-devel-general@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Florian Fainelli <florian@...nwrt.org>
Subject: [RFC PATCH] spi/bcm63xx: Ensure that memory is freed only after it is no longer used

The call to spi_unregister_master() in the device remove function frees device
memory, and with it any device local data. However, device local data is still
accessed after the call to spi_unregister_master().

Acquire a reference to the SPI device and release it after cleanup is complete
to solve the problem.

Cc: Florian Fainelli <florian@...nwrt.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
Several drivers have this problem, and I am trying to find a common fix.

This solution is modeled after the approach used in spi-txx9spi:txx9spi_remove.
The other possible fix would be to move spi_unregister_master() to the end of
bcm63xx_spi_remove(), but I am not sure if it is a good idea to clean up
before the call to spi_unregister_master().

 drivers/spi/spi-bcm63xx.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm63xx.c b/drivers/spi/spi-bcm63xx.c
index 6e25ef1..ea0aaa3 100644
--- a/drivers/spi/spi-bcm63xx.c
+++ b/drivers/spi/spi-bcm63xx.c
@@ -438,7 +438,7 @@ out:
 
 static int __devexit bcm63xx_spi_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = platform_get_drvdata(pdev);
+	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
 	struct bcm63xx_spi *bs = spi_master_get_devdata(master);
 
 	spi_unregister_master(master);
@@ -452,6 +452,8 @@ static int __devexit bcm63xx_spi_remove(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, 0);
 
+	spi_master_put(master);
+
 	return 0;
 }
 
-- 
1.7.9.7

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