linux-kernel - [PATCH 4.10 034/167] staging: greybus: loopback: fix broken udelay

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Date:   Fri, 10 Mar 2017 10:07:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH 4.10 034/167] staging: greybus: loopback: fix broken udelay

4.10-stable review patch.  If anyone has any objections, please let me know.

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

From: Johan Hovold <johan@...nel.org>

commit 33b8807a6fe10d0e675e0704444373a6fad93188 upstream.

The loopback driver allows the user to set a minimum delay of up to one
second to be inserted between test iterations (i.e. request
submissions). The delay is currently specified in microseconds and is
implemented using udelay.

Busy looping for long periods is not just anti-social; udelay must not
be used for delays longer than a few milliseconds due to the risk of
integer overflow.

Replace the broken udelay with a usleep_range with a 100 us range for
short delays (< 20 ms) and otherwise revert to using msleep.

Fixes: b36f04fa9417 ("greybus: loopback: Convert thread delay to microseconds")
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/greybus/loopback.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -1051,8 +1051,13 @@ static int gb_loopback_fn(void *data)
 			gb_loopback_calculate_stats(gb, !!error);
 		}
 		gb->send_count++;
-		if (us_wait)
-			udelay(us_wait);
+
+		if (us_wait) {
+			if (us_wait < 20000)
+				usleep_range(us_wait, us_wait + 100);
+			else
+				msleep(us_wait / 1000);
+		}
 	}

 	gb_pm_runtime_put_autosuspend(bundle);