linux-kernel - [PATCH 3.4 51/92] spi: Fix documentation of spi_alloc

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Date:	Mon, 18 Apr 2016 18:45:56 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
	Alexey Klimov <alexey.klimov@...aro.org>,
	Mark Brown <broonie@...nel.org>, Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 51/92] spi: Fix documentation of spi_alloc_master()

From: Guenter Roeck <linux@...ck-us.net>

3.4.112-rc1 review patch.  If anyone has any objections, please let me know.

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

commit a394d635193b641f2c86ead5ada5b115d57c51f8 upstream.

Actually, spi_master_put() after spi_alloc_master() must _not_ be followed
by kfree(). The memory is already freed with the call to spi_master_put()
through spi_master_class, which registers a release function. Calling both
spi_master_put() and kfree() results in often nasty (and delayed) crashes
elsewhere in the kernel, often in the networking stack.

This reverts commit eb4af0f5349235df2e4a5057a72fc8962d00308a.

Link to patch and concerns: https://lkml.org/lkml/2012/9/3/269
or
http://lkml.iu.edu/hypermail/linux/kernel/1209.0/00790.html

Alexey Klimov: This revert becomes valid after
94c69f765f1b4a658d96905ec59928e3e3e07e6a when spi-imx.c
has been fixed and there is no need to call kfree() so comment
for spi_alloc_master() should be fixed.

Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Signed-off-by: Alexey Klimov <alexey.klimov@...aro.org>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 drivers/spi/spi.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 3d8f662..a3f31e9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -831,8 +831,7 @@ static struct class spi_master_class = {
  *
  * The caller is responsible for assigning the bus number and initializing
  * the master's methods before calling spi_register_master(); and (after errors
- * adding the device) calling spi_master_put() and kfree() to prevent a memory
- * leak.
+ * adding the device) calling spi_master_put() to prevent a memory leak.
  */
 struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
 {
-- 
1.9.1