Patch "staging: greybus: loopback: fix broken udelay" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    staging: greybus: loopback: fix broken udelay

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     staging-greybus-loopback-fix-broken-udelay.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 33b8807a6fe10d0e675e0704444373a6fad93188 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Thu, 26 Jan 2017 12:37:32 +0100
Subject: staging: greybus: loopback: fix broken udelay

From: Johan Hovold <johan@kernel.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@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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);


Patches currently in stable-queue which might be from johan@kernel.org are

queue-4.9/staging-greybus-loopback-fix-broken-udelay.patch