linux-kernel - [PATCH] usb: storage: Replace mdelay with msleep in init

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Date:   Tue, 10 Apr 2018 09:29:08 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     stern@...land.harvard.edu, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, usb-storage@...ts.one-eyed-alien.net,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] usb: storage: Replace mdelay with msleep in init_freecom

init_freecom() is never called in atomic context.

init_freecom() is set as ".initFunction" through UNUSUAL_DEV().
And ->initFunction() is only called by usb_stor_acquire_resources(), 
which is only called by usb_stor_probe2().
usb_stor_probe2() is called by *_probe() functions (like alauda_probe()) 
for each USB driver.
*_probe() functions are set ".probe" in struct usb_driver.
These functions are not called in atomic context.

Despite never getting called from atomic context, init_freecom()
calls mdelay() to busily wait.
This is not necessary and can be replaced with msleep() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/usb/storage/freecom.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/storage/freecom.c b/drivers/usb/storage/freecom.c
index c0a5d95..c7f886d 100644
--- a/drivers/usb/storage/freecom.c
+++ b/drivers/usb/storage/freecom.c
@@ -477,7 +477,7 @@ static int init_freecom(struct us_data *us)
 	usb_stor_dbg(us, "result from activate reset is %d\n", result);

 	/* wait 250ms */
-	mdelay(250);
+	msleep(250);

 	/* clear reset */
 	result = usb_stor_control_msg(us, us->send_ctrl_pipe,
@@ -485,7 +485,7 @@ static int init_freecom(struct us_data *us)
 	usb_stor_dbg(us, "result from clear reset is %d\n", result);

 	/* wait 3 seconds */
-	mdelay(3 * 1000);
+	msleep(3 * 1000);

 	return USB_STOR_TRANSPORT_GOOD;
 }
-- 
1.9.1