[PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq

[PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq

[Dave Martin]

pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
sufficient to inhibit pl011_int() from being triggered by a local
IRQ and trying to re-take the same lock.  This can lead to
deadlocks.

This patch uses the _irq() locking variants instead to ensure that
pl011_int() handling for a given port is deferred until any
pl011_tx_softirq() work for that port is complete.


Notes for stable:

This patch fixes an issue that is fixed by the following upstream
commit, which is a more substantial rewrite of the affected code,
fixing multiple, mostly more minor issues:

        1e84d22322ceed4767db1e5342c830dd60c8210f
        serial/amba-pl011: Refactor and simplify TX FIFO handling

The upstream patch was rejected for stable on the reasonable grounds
that it was too big and complex a patch.  The original buggy code was
merged in v4.1, and the rewrite was merged in v4.2, leaving only v4.1
affected.


This patch replaces the 1e84d22, for 4.1.x only.

Fixes: 734745caeb9f serial/amba-pl011: Activate TX IRQ passively
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: stable <stable@vger.kernel.org> # 4.1.x
---
 drivers/tty/serial/amba-pl011.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 763eb20..0cc622a 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1360,9 +1360,9 @@ static void pl011_tx_softirq(struct work_struct *work)
 	struct uart_amba_port *uap =
 		container_of(dwork, struct uart_amba_port, tx_softirq_work);
 
-	spin_lock(&uap->port.lock);
+	spin_lock_irq(&uap->port.lock);
 	while (pl011_tx_chars(uap)) ;
-	spin_unlock(&uap->port.lock);
+	spin_unlock_irq(&uap->port.lock);
 }
 
 static void pl011_tx_irq_seen(struct uart_amba_port *uap)
-- 
1.7.10.4

[PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq

[Dave Martin]

pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
sufficient to inhibit pl011_int() from being triggered by a local
IRQ and trying to re-take the same lock.  This can lead to
deadlocks.

This patch uses the _irq() locking variants instead to ensure that
pl011_int() handling for a given port is deferred until any
pl011_tx_softirq() work for that port is complete.


Notes for stable:

This patch fixes an issue that is fixed by the following upstream
commit, which is a more substantial rewrite of the affected code,
fixing multiple, mostly more minor issues:

        1e84d22322ceed4767db1e5342c830dd60c8210f
        serial/amba-pl011: Refactor and simplify TX FIFO handling

The upstream patch was rejected for stable on the reasonable grounds
that it was too big and complex a patch.  The original buggy code was
merged in v4.1, and the rewrite was merged in v4.2, leaving only v4.1
affected.


This patch replaces the 1e84d22, for 4.1.x only.

Fixes: 734745caeb9f serial/amba-pl011: Activate TX IRQ passively
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Cc: stable <stable@vger.kernel.org> # 4.1.x
---
 drivers/tty/serial/amba-pl011.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 763eb20..0cc622a 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1360,9 +1360,9 @@ static void pl011_tx_softirq(struct work_struct *work)
 	struct uart_amba_port *uap =
 		container_of(dwork, struct uart_amba_port, tx_softirq_work);
 
-	spin_lock(&uap->port.lock);
+	spin_lock_irq(&uap->port.lock);
 	while (pl011_tx_chars(uap)) ;
-	spin_unlock(&uap->port.lock);
+	spin_unlock_irq(&uap->port.lock);
 }
 
 static void pl011_tx_irq_seen(struct uart_amba_port *uap)
-- 
1.7.10.4

Patch "[PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq" has been added to the 4.1-stable tree

[gregkh]

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

    [PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq

to the 4.1-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:
     serial-amba-pl011-disable-interrupts-around-tx-softirq.patch
and it can be found in the queue-4.1 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 Dave.Martin@arm.com  Sat Oct 17 13:59:05 2015
From: Dave Martin <Dave.Martin@arm.com>
Date: Fri, 24 Jul 2015 17:39:21 +0100
Subject: [PATCH REPOST] serial/amba-pl011: Disable interrupts around TX softirq
To: linux-serial@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Russell King <linux@arm.linux.org.uk>, Robin Murphy <Robin.Murphy@arm.com>, linux-arm-kernel@lists.infradead.org, Jakub Kiciński <moorray3@wp.pl>, Andrew Jackson <Andrew.Jackson@arm.com>, Graeme Gregory <gg@slimlogic.co.uk>, Andre Przywara <Andre.Przywara@arm.com>, Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>, popcorn mix <popcornmix@gmail.com>, stable <stable@vger.kernel.org>
Message-ID: <1437755961-15403-1-git-send-email-Dave.Martin@arm.com>

From: Dave Martin <Dave.Martin@arm.com>

pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
sufficient to inhibit pl011_int() from being triggered by a local
IRQ and trying to re-take the same lock.  This can lead to
deadlocks.

This patch uses the _irq() locking variants instead to ensure that
pl011_int() handling for a given port is deferred until any
pl011_tx_softirq() work for that port is complete.


Notes for stable:

This patch fixes an issue that is fixed by the following upstream
commit, which is a more substantial rewrite of the affected code,
fixing multiple, mostly more minor issues:

        1e84d22322ceed4767db1e5342c830dd60c8210f
        serial/amba-pl011: Refactor and simplify TX FIFO handling

The upstream patch was rejected for stable on the reasonable grounds
that it was too big and complex a patch.  The original buggy code was
merged in v4.1, and the rewrite was merged in v4.2, leaving only v4.1
affected.


This patch replaces the 1e84d22, for 4.1.x only.

Fixes: 734745caeb9f serial/amba-pl011: Activate TX IRQ passively
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/amba-pl011.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1360,9 +1360,9 @@ static void pl011_tx_softirq(struct work
 	struct uart_amba_port *uap =
 		container_of(dwork, struct uart_amba_port, tx_softirq_work);
 
-	spin_lock(&uap->port.lock);
+	spin_lock_irq(&uap->port.lock);
 	while (pl011_tx_chars(uap)) ;
-	spin_unlock(&uap->port.lock);
+	spin_unlock_irq(&uap->port.lock);
 }
 
 static void pl011_tx_irq_seen(struct uart_amba_port *uap)


Patches currently in stable-queue which might be from Dave.Martin@arm.com are

queue-4.1/serial-amba-pl011-disable-interrupts-around-tx-softirq.patch