linux-kernel - [PATCH 3.16.y-ckt 004/216] s390/3215: fix hanging console issue

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Date:	Mon, 12 Jan 2015 18:02:01 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 004/216] s390/3215: fix hanging console issue

3.16.7-ckt4 -stable review patch.  If anyone has any objections, please let me know.

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

From: Martin Schwidefsky <schwidefsky@...ibm.com>

commit 26d766c60f4ea08cd14f0f3435a6db3d6cc2ae96 upstream.

The ccw_device_start in raw3215_start_io can fail. raw3215_try_io
does not check if the request could be started and removes any
pending timer. This can leave the system in a hanging state.
Check for pending request after raw3215_start_io and start a
timer if necessary.

Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/s390/char/con3215.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
index 5af7f0bd6125..a6d47e5eee9e 100644
--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -288,12 +288,16 @@ static void raw3215_timeout(unsigned long __data)
 	unsigned long flags;
 
 	spin_lock_irqsave(get_ccwdev_lock(raw->cdev), flags);
-	if (raw->flags & RAW3215_TIMER_RUNS) {
-		del_timer(&raw->timer);
-		raw->flags &= ~RAW3215_TIMER_RUNS;
-		if (!(raw->port.flags & ASYNC_SUSPENDED)) {
-			raw3215_mk_write_req(raw);
-			raw3215_start_io(raw);
+	raw->flags &= ~RAW3215_TIMER_RUNS;
+	if (!(raw->port.flags & ASYNC_SUSPENDED)) {
+		raw3215_mk_write_req(raw);
+		raw3215_start_io(raw);
+		if ((raw->queued_read || raw->queued_write) &&
+		    !(raw->flags & RAW3215_WORKING) &&
+		    !(raw->flags & RAW3215_TIMER_RUNS)) {
+			raw->timer.expires = RAW3215_TIMEOUT + jiffies;
+			add_timer(&raw->timer);
+			raw->flags |= RAW3215_TIMER_RUNS;
 		}
 	}
 	spin_unlock_irqrestore(get_ccwdev_lock(raw->cdev), flags);
@@ -317,17 +321,15 @@ static inline void raw3215_try_io(struct raw3215_info *raw)
 		    (raw->flags & RAW3215_FLUSHING)) {
 			/* execute write requests bigger than minimum size */
 			raw3215_start_io(raw);
-			if (raw->flags & RAW3215_TIMER_RUNS) {
-				del_timer(&raw->timer);
-				raw->flags &= ~RAW3215_TIMER_RUNS;
-			}
-		} else if (!(raw->flags & RAW3215_TIMER_RUNS)) {
-			/* delay small writes */
-			raw->timer.expires = RAW3215_TIMEOUT + jiffies;
-			add_timer(&raw->timer);
-			raw->flags |= RAW3215_TIMER_RUNS;
 		}
 	}
+	if ((raw->queued_read || raw->queued_write) &&
+	    !(raw->flags & RAW3215_WORKING) &&
+	    !(raw->flags & RAW3215_TIMER_RUNS)) {
+		raw->timer.expires = RAW3215_TIMEOUT + jiffies;
+		add_timer(&raw->timer);
+		raw->flags |= RAW3215_TIMER_RUNS;
+	}
 }
 
 /*
-- 
2.1.4

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