linux-kernel - [PATCH 4/7] Char: moxa, fix locking in moxa

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Date:	Wed, 20 Apr 2011 10:43:15 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	gregkh@...e.de
Cc:	jirislaby@...il.com, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH 4/7] Char: moxa, fix locking in moxa_write

moxa_write can be called from atomic context with irqs disabled (from
ppp_async_push). Don't enable interrupts by spin_unlock_bh as this
might cause deadlocks in the ppp layer.

Instead, use irqsave/irqrestore spin_lock functions.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/tty/moxa.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index a290e9e..6255561 100644
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -1202,14 +1202,15 @@ static int moxa_write(struct tty_struct *tty,
 		      const unsigned char *buf, int count)
 {
 	struct moxa_port *ch = tty->driver_data;
+	unsigned long flags;
 	int len;
 
 	if (ch == NULL)
 		return 0;
 
-	spin_lock_bh(&moxa_lock);
+	spin_lock_irqsave(&moxa_lock, flags);
 	len = MoxaPortWriteData(tty, buf, count);
-	spin_unlock_bh(&moxa_lock);
+	spin_unlock_irqrestore(&moxa_lock, flags);
 
 	set_bit(LOWWAIT, &ch->statusflags);
 	return len;
-- 
1.7.4.2


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