linux-kernel - [PATCH v2 4/9] pps: Don't crash the machine when exiting will do

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Date:	Sun, 10 Feb 2013 04:43:41 -0500
From:	George Spelvin <linux@...izon.com>
To:	linux-serial@...r.kernel.org, peter@...leysoftware.com,
	gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, giometti@...ux.it, linux@...izon.com
Subject: [PATCH v2 4/9] pps: Don't crash the machine when exiting will do

PPS is not really the must-have subsystem that warrants crashing
the machine if the ldisc interface is broken.

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
Signed-off-by: George Spelvin <linux@...izon.com>
---
 drivers/pps/clients/pps-ldisc.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c
index 60cee9e..a94f73e 100644
--- a/drivers/pps/clients/pps-ldisc.c
+++ b/drivers/pps/clients/pps-ldisc.c
@@ -25,6 +25,7 @@
 #include <linux/serial_core.h>
 #include <linux/tty.h>
 #include <linux/pps_kernel.h>
+#include <linux/bug.h>
 
 #define PPS_TTY_MAGIC		0x0001
 
@@ -33,7 +34,12 @@ static void pps_tty_dcd_change(struct tty_struct *tty, unsigned int status,
 {
 	struct pps_device *pps = pps_lookup_dev(tty);
 
-	BUG_ON(pps == NULL);
+	/*
+	 * This should never fail, but the ldisc locking is very
+	 * convoluted, so don't crash just in case.
+	 */
+	if (WARN_ON_ONCE(pps == NULL))
+		return;
 
 	/* Now do the PPS event report */
 	pps_event(pps, ts, status ? PPS_CAPTUREASSERT :
@@ -93,6 +99,9 @@ static void pps_tty_close(struct tty_struct *tty)
 
 	alias_n_tty_close(tty);
 
+	if (WARN_ON(!pps))
+		return;
+
 	dev_info(pps->dev, "removed\n");
 	pps_unregister_source(pps);
 }
-- 
1.8.1.3

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