From: Dave.Martin@arm.com (Dave Martin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] serial/amba-pl011: Disable interrupts around TX softirq
Date: Fri, 5 Jun 2015 15:07:47 +0100 [thread overview]
Message-ID: <1433513267-24163-1-git-send-email-Dave.Martin@arm.com> (raw)
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.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
Another candidate for v4.1 if possible (sorry!) -- I thought this change
was already in, but it went astray when I was refactoring.
This patch conflicts with tty-next like the previous patch, since it
fixes code that is removed by tty-next. The correct resolution for
the resulting merge conflict is to keep the code from tty-next.
I am not 100% certain yet whether some rare deadlocks that Robin is
seeing are caused by this issue, or whether this patch fixes them --
he's testing atm.
The patch is straightforward and using non _irq() locking in a workitem
that expects the lock to protect against interrupt handlers on the same
CPU is clearly wrong.
Cheers
---Dave
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
WARNING: multiple messages have this Message-ID (diff)
From: Dave Martin <Dave.Martin@arm.com>
To: linux-serial@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Russell King" <linux@arm.linux.org.uk>,
"Jakub Kiciński" <moorray3@wp.pl>,
"Andre Przywara" <Andre.Przywara@arm.com>,
"Andrew Jackson" <Andrew.Jackson@arm.com>,
"Graeme Gregory" <gg@slimlogic.co.uk>,
"popcorn mix" <popcornmix@gmail.com>,
"Jorge Ramirez-Ortiz" <jorge.ramirez-ortiz@linaro.org>,
"Robin Murphy" <Robin.Murphy@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH] serial/amba-pl011: Disable interrupts around TX softirq
Date: Fri, 5 Jun 2015 15:07:47 +0100 [thread overview]
Message-ID: <1433513267-24163-1-git-send-email-Dave.Martin@arm.com> (raw)
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.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
Another candidate for v4.1 if possible (sorry!) -- I thought this change
was already in, but it went astray when I was refactoring.
This patch conflicts with tty-next like the previous patch, since it
fixes code that is removed by tty-next. The correct resolution for
the resulting merge conflict is to keep the code from tty-next.
I am not 100% certain yet whether some rare deadlocks that Robin is
seeing are caused by this issue, or whether this patch fixes them --
he's testing atm.
The patch is straightforward and using non _irq() locking in a workitem
that expects the lock to protect against interrupt handlers on the same
CPU is clearly wrong.
Cheers
---Dave
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
next reply other threads:[~2015-06-05 14:07 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-05 14:07 Dave Martin [this message]
2015-06-05 14:07 ` [PATCH] serial/amba-pl011: Disable interrupts around TX softirq Dave Martin
2015-06-05 18:03 ` Robin Murphy
2015-06-05 18:03 ` Robin Murphy
2015-06-08 10:34 ` Robin Murphy
2015-06-08 10:34 ` Robin Murphy
2015-06-08 11:34 ` Dave P Martin
2015-06-08 11:34 ` Dave P Martin
2015-06-13 0:39 ` Greg Kroah-Hartman
2015-06-13 0:39 ` Greg Kroah-Hartman
2015-06-15 10:53 ` Dave P Martin
2015-06-15 10:53 ` Dave P Martin
2015-06-15 11:09 ` Andre Przywara
2015-06-15 11:09 ` Andre Przywara
2015-06-15 14:03 ` Dave Martin
2015-06-15 14:03 ` Dave Martin
-- strict thread matches above, loose matches on Subject: below --
2015-06-18 13:54 Dave Martin
2015-06-18 13:54 ` Dave Martin
2015-06-20 9:09 ` Stefan Wahren
2015-06-20 9:09 ` Stefan Wahren
2015-06-20 9:09 ` Stefan Wahren
2015-06-23 11:13 ` Dave P Martin
2015-06-23 11:13 ` Dave P Martin
2015-07-09 10:57 Dave Martin
2015-07-09 10:57 ` Dave Martin
2015-07-23 22:05 ` Greg Kroah-Hartman
2015-07-23 22:05 ` Greg Kroah-Hartman
2015-07-24 9:56 ` Dave Martin
2015-07-24 9:56 ` Dave Martin
2015-07-24 15:15 ` Greg Kroah-Hartman
2015-07-24 15:15 ` Greg Kroah-Hartman
2015-07-24 16:46 ` Dave Martin
2015-07-24 16:46 ` Dave Martin
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