linux-kernel - [PATCH 3.19 105/177] serial: 8250: Revert "tty: serial: 8250_core: read only RX if there is something in the FIFO"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20150316140817.862181237@linuxfoundation.org>
Date:	Mon, 16 Mar 2015 15:08:32 +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, Nicolas Schichan <nschichan@...ebox.fr>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 3.19 105/177] serial: 8250: Revert "tty: serial: 8250_core: read only RX if there is something in the FIFO"

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

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

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

commit ca8bb4aefb932e3da105f28cbfba36d57a931081 upstream.

This reverts commit 0aa525d11859c1a4d5b78fdc704148e2ae03ae13.

The conditional RX-FIFO read seems to cause spurious interrupts and we
see just:
|serial8250: too much work for irq29

The previous behaviour was "default" for decades and Marvell's 88f6282 SoC
might not be the only that relies on it. Therefore the Omap fix is
reverted for now.

Fixes: 0aa525d11859 ("tty: serial: 8250_core: read only RX if there is
something in the FIFO")
Reported-By: Nicolas Schichan <nschichan@...ebox.fr>
Debuged-By: Peter Hurley <peter@...leysoftware.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/8250/8250_core.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2107,8 +2107,8 @@ int serial8250_do_startup(struct uart_po
 	/*
 	 * Clear the interrupt registers.
 	 */
-	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)
-		serial_port_in(port, UART_RX);
+	serial_port_in(port, UART_LSR);
+	serial_port_in(port, UART_RX);
 	serial_port_in(port, UART_IIR);
 	serial_port_in(port, UART_MSR);
 
@@ -2269,8 +2269,8 @@ dont_test_tx_en:
 	 * saved flags to avoid getting false values from polling
 	 * routines or the previous session.
 	 */
-	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)
-		serial_port_in(port, UART_RX);
+	serial_port_in(port, UART_LSR);
+	serial_port_in(port, UART_RX);
 	serial_port_in(port, UART_IIR);
 	serial_port_in(port, UART_MSR);
 	up->lsr_saved_flags = 0;
@@ -2363,8 +2363,7 @@ void serial8250_do_shutdown(struct uart_
 	 * Read data port to reset things, and then unlink from
 	 * the IRQ chain.
 	 */
-	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)
-		serial_port_in(port, UART_RX);
+	serial_port_in(port, UART_RX);
 	serial8250_rpm_put(up);
 
 	del_timer_sync(&up->timer);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/