linux-kernel - [PATCH] firmware loader: Fix the race FW_STATUS_DONE is followed by class

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Date:	Thu, 08 Nov 2012 00:45:44 +0800
From:	Chuansheng Liu <chuansheng.liu@...el.com>
To:	ming.lei@...onical.com, gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, chuansheng.liu@...el.com
Subject: [PATCH] firmware loader: Fix the race FW_STATUS_DONE is followed
 by class_timeout


There is a race condition as below when calling request_firmware():

CPU1					CPU2
write 0 > loading
mutex_lock(&fw_lock);
...
set_bit FW_STATUS_DONE                  class_timeout is coming
					set_bit FW_STATUS_ABORT
complete_all &completion
...
mutex_unlock(&fw_lock)

In this time, the bit FW_STATUS_DONE and FW_STATUS_ABORT are set,
and request_firmware() will return failure due to condition in
_request_firmware_load():

	if (!buf->size || test_bit(FW_STATUS_ABORT, &buf->status))
		retval = -ENOENT;

But from the above scenerio, it should be a succcessful requesting.
So we need judge if the FW_STATUS_DONE is set before calling abort
in timeout function firmware_class_timeout().

Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
---
 drivers/base/firmware_class.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 8945f4e..35fffd8 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -671,6 +671,13 @@ static void firmware_class_timeout(u_long data)
 {
 	struct firmware_priv *fw_priv = (struct firmware_priv *) data;
 
+	mutex_lock(&fw_lock);
+	if (test_bit(FW_STATUS_DONE, &(fw_priv->buf->status))) {
+		mutex_unlock(&fw_lock);
+		return;
+	}
+	mutex_unlock(&fw_lock);
+
 	fw_load_abort(fw_priv);
 }
 
-- 
1.7.0.4



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