linux-kernel - [PATCH v3] staging: r8188eu: Remove _enter/_exit_critical

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Message-Id: <20210819221241.31987-1-fmdefrancesco@gmail.com>
Date:   Fri, 20 Aug 2021 00:12:41 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Martin Kaiser <martin@...ser.cx>,
        Michael Straube <straube.linux@...il.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Subject: [PATCH v3] staging: r8188eu: Remove _enter/_exit_critical_mutex()

Remove _enter_critical_mutex() and _exit_critical_mutex(). They are
unnecessary wrappers, respectively to mutex_lock_interruptible() and
to mutex_unlock(). They also have an odd interface that takes an unused
argument named pirqL of type unsigned long.
The original code enters the critical section if the mutex API is
interrupted while waiting to acquire the lock; therefore it could lead
to a race condition. Use mutex_lock() because it is uninterruptible and
so avoid that above-mentioned potential race condition.

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---

v3: Assume that the original authors don't expect that
mutex_lock_interruptible() can be really interrupted and then lead to 
a potential race condition. Furthermore, Greg Kroah-Hartman makes me
notice that "[] one almost never needs interruptable locks in a driver".
Therefore, replace the calls to mutex_lock_interruptible() with calls to
mutex_lock() since the latter is uninterruptible and avoid race
conditions without the necessity to handle -EINTR errors.

v2: Ignore return values from Mutexes API because the original authors
don't check and manage return errors from mutex_lock_interruptible(). 

 drivers/staging/r8188eu/core/rtw_mlme_ext.c     |  4 ++--
 drivers/staging/r8188eu/hal/usb_ops_linux.c     |  4 ++--
 drivers/staging/r8188eu/include/osdep_service.h | 13 -------------
 drivers/staging/r8188eu/os_dep/os_intfs.c       |  4 ++--
 4 files changed, 6 insertions(+), 19 deletions(-)

diff --git a/drivers/staging/r8188eu/core/rtw_mlme_ext.c b/drivers/staging/r8188eu/core/rtw_mlme_ext.c
index 5325fe41fbee..873b54c1715f 100644
--- a/drivers/staging/r8188eu/core/rtw_mlme_ext.c
+++ b/drivers/staging/r8188eu/core/rtw_mlme_ext.c
@@ -4359,7 +4359,7 @@ s32 dump_mgntframe_and_wait_ack(struct adapter *padapter, struct xmit_frame *pmg
 	if (padapter->bSurpriseRemoved || padapter->bDriverStopped)
 		return -1;
 
-	_enter_critical_mutex(&pxmitpriv->ack_tx_mutex, NULL);
+	mutex_lock(&pxmitpriv->ack_tx_mutex);
 	pxmitpriv->ack_tx = true;
 
 	pmgntframe->ack_report = 1;
@@ -4368,7 +4368,7 @@ s32 dump_mgntframe_and_wait_ack(struct adapter *padapter, struct xmit_frame *pmg
 	}
 
 	pxmitpriv->ack_tx = false;
-	_exit_critical_mutex(&pxmitpriv->ack_tx_mutex, NULL);
+	mutex_unlock(&pxmitpriv->ack_tx_mutex);
 
 	return ret;
 }
diff --git a/drivers/staging/r8188eu/hal/usb_ops_linux.c b/drivers/staging/r8188eu/hal/usb_ops_linux.c
index 953fa05dc30c..a93d5cfe4635 100644
--- a/drivers/staging/r8188eu/hal/usb_ops_linux.c
+++ b/drivers/staging/r8188eu/hal/usb_ops_linux.c
@@ -32,7 +32,7 @@ static int usbctrl_vendorreq(struct intf_hdl *pintfhdl, u16 value, void *pdata,
 		goto exit;
 	}
 
-	_enter_critical_mutex(&dvobjpriv->usb_vendor_req_mutex, NULL);
+	mutex_lock(&dvobjpriv->usb_vendor_req_mutex);
 
 	/*  Acquire IO memory for vendorreq */
 	pIo_buf = dvobjpriv->usb_vendor_req_buf;
@@ -96,7 +96,7 @@ static int usbctrl_vendorreq(struct intf_hdl *pintfhdl, u16 value, void *pdata,
 			break;
 	}
 release_mutex:
-	_exit_critical_mutex(&dvobjpriv->usb_vendor_req_mutex, NULL);
+	mutex_unlock(&dvobjpriv->usb_vendor_req_mutex);
 exit:
 	return status;
 }
diff --git a/drivers/staging/r8188eu/include/osdep_service.h b/drivers/staging/r8188eu/include/osdep_service.h
index 029aa4e92c9b..bb92b9d74bd7 100644
--- a/drivers/staging/r8188eu/include/osdep_service.h
+++ b/drivers/staging/r8188eu/include/osdep_service.h
@@ -56,19 +56,6 @@ static inline struct list_head *get_list_head(struct __queue *queue)
 	return (&(queue->queue));
 }
 
-static inline int _enter_critical_mutex(struct mutex *pmutex, unsigned long *pirqL)
-{
-	int ret;
-
-	ret = mutex_lock_interruptible(pmutex);
-	return ret;
-}
-
-static inline void _exit_critical_mutex(struct mutex *pmutex, unsigned long *pirqL)
-{
-		mutex_unlock(pmutex);
-}
-
 static inline void rtw_list_delete(struct list_head *plist)
 {
 	list_del_init(plist);
diff --git a/drivers/staging/r8188eu/os_dep/os_intfs.c b/drivers/staging/r8188eu/os_dep/os_intfs.c
index 1aa65925e1da..e675e4e9550e 100644
--- a/drivers/staging/r8188eu/os_dep/os_intfs.c
+++ b/drivers/staging/r8188eu/os_dep/os_intfs.c
@@ -1065,9 +1065,9 @@ int netdev_open(struct net_device *pnetdev)
 	int ret;
 	struct adapter *padapter = (struct adapter *)rtw_netdev_priv(pnetdev);
 
-	_enter_critical_mutex(padapter->hw_init_mutex, NULL);
+	mutex_lock(padapter->hw_init_mutex);
 	ret = _netdev_open(pnetdev);
-	_exit_critical_mutex(padapter->hw_init_mutex, NULL);
+	mutex_unlock(padapter->hw_init_mutex);
 	return ret;
 }
 
-- 
2.32.0