linux-kernel - [PATCH 1/2] staging: irda: Replace mdelay with usleep_range in stir421x_fw

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Message-Id: <1523410174-1553-1-git-send-email-baijiaju1990@gmail.com>
Date:   Wed, 11 Apr 2018 09:29:34 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     samuel@...tiz.org, gregkh@...uxfoundation.org, davem@...emloft.net,
        johan@...nel.org, arvind.yadav.cs@...il.com
Cc:     netdev@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 1/2] staging: irda: Replace mdelay with usleep_range in stir421x_fw_upload

stir421x_fw_upload() is never called in atomic context.

The call chain ending up at stir421x_fw_upload() is:
[1] stir421x_fw_upload() <- stir421x_patch_device() <- irda_usb_probe()

irda_usb_probe() is set as ".probe" in struct usb_driver.
This function is not called in atomic context.

Despite never getting called from atomic context, stir421x_fw_upload()
calls mdelay() to busily wait.
This is not necessary and can be replaced with usleep_range() 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/staging/irda/drivers/irda-usb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/irda/drivers/irda-usb.c b/drivers/staging/irda/drivers/irda-usb.c
index 723e49b..c6c8c2c 100644
--- a/drivers/staging/irda/drivers/irda-usb.c
+++ b/drivers/staging/irda/drivers/irda-usb.c
@@ -1050,7 +1050,7 @@ static int stir421x_fw_upload(struct irda_usb_cb *self,
 		if (ret < 0)
 			break;
 
-		mdelay(10);
+		usleep_range(10000, 11000);
 	}
 
 	kfree(patch_block);
-- 
1.9.1