* [PATCH 1/3] serial: do not restore interrupt state in sysrq helper
2021-04-16 14:05 [PATCH 0/3] serial: sysrq cleanup and stm32 fixes Johan Hovold
@ 2021-04-16 14:05 ` Johan Hovold
2021-04-16 14:05 ` [PATCH 2/3] serial: stm32: fix threaded interrupt handling Johan Hovold
2021-04-16 14:05 ` [PATCH 3/3] serial: stm32: defer sysrq processing Johan Hovold
2 siblings, 0 replies; 8+ messages in thread
From: Johan Hovold @ 2021-04-16 14:05 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, dillon.minfei,
Erwan Le Ray, linux-serial, linux-kernel, Johan Hovold,
Joel Stanley, Andrew Jeffery, Andy Gross, Bjorn Andersson
The uart_unlock_and_check_sysrq() helper can be used to defer processing
of sysrq until the interrupt handler has released the port lock and is
about to return.
Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers that are not explicitly requested
as threaded are always called with interrupts disabled and there is no
need to save the interrupt state when taking the port lock.
Instead of adding another sysrq helper for when the interrupt state has
not needlessly been saved, drop the state parameter from
uart_unlock_and_check_sysrq() and update its callers to no longer
explicitly disable interrupts in their interrupt handlers.
Cc: Joel Stanley <joel@jms.id.au>
Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/serial/8250/8250_aspeed_vuart.c | 5 ++---
drivers/tty/serial/8250/8250_fsl.c | 11 ++++++-----
drivers/tty/serial/8250/8250_omap.c | 6 +++---
drivers/tty/serial/8250/8250_port.c | 6 +++---
drivers/tty/serial/qcom_geni_serial.c | 6 +++---
include/linux/serial_core.h | 10 +++++-----
6 files changed, 22 insertions(+), 22 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c
index 3c239d98747f..61550f24a2d3 100644
--- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
+++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
@@ -320,7 +320,6 @@ static int aspeed_vuart_handle_irq(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
unsigned int iir, lsr;
- unsigned long flags;
int space, count;
iir = serial_port_in(port, UART_IIR);
@@ -328,7 +327,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port)
if (iir & UART_IIR_NO_INT)
return 0;
- spin_lock_irqsave(&port->lock, flags);
+ spin_lock(&port->lock);
lsr = serial_port_in(port, UART_LSR);
@@ -364,7 +363,7 @@ static int aspeed_vuart_handle_irq(struct uart_port *port)
if (lsr & UART_LSR_THRE)
serial8250_tx_chars(up);
- uart_unlock_and_check_sysrq(port, flags);
+ uart_unlock_and_check_sysrq(port);
return 1;
}
diff --git a/drivers/tty/serial/8250/8250_fsl.c b/drivers/tty/serial/8250/8250_fsl.c
index cd19400b65ae..4e75d2e4f87c 100644
--- a/drivers/tty/serial/8250/8250_fsl.c
+++ b/drivers/tty/serial/8250/8250_fsl.c
@@ -30,15 +30,14 @@ struct fsl8250_data {
int fsl8250_handle_irq(struct uart_port *port)
{
unsigned char lsr, orig_lsr;
- unsigned long flags;
unsigned int iir;
struct uart_8250_port *up = up_to_u8250p(port);
- spin_lock_irqsave(&up->port.lock, flags);
+ spin_lock(&up->port.lock);
iir = port->serial_in(port, UART_IIR);
if (iir & UART_IIR_NO_INT) {
- spin_unlock_irqrestore(&up->port.lock, flags);
+ spin_unlock(&up->port.lock);
return 0;
}
@@ -46,7 +45,7 @@ int fsl8250_handle_irq(struct uart_port *port)
if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
up->lsr_saved_flags &= ~UART_LSR_BI;
port->serial_in(port, UART_RX);
- spin_unlock_irqrestore(&up->port.lock, flags);
+ spin_unlock(&up->port.lock);
return 1;
}
@@ -82,7 +81,9 @@ int fsl8250_handle_irq(struct uart_port *port)
serial8250_tx_chars(up);
up->lsr_saved_flags = orig_lsr;
- uart_unlock_and_check_sysrq(&up->port, flags);
+
+ uart_unlock_and_check_sysrq(&up->port);
+
return 1;
}
EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 23e0decde33e..8ac11eaeca51 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1143,7 +1143,6 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
struct uart_8250_port *up = up_to_u8250p(port);
struct omap8250_priv *priv = up->port.private_data;
unsigned char status;
- unsigned long flags;
u8 iir;
serial8250_rpm_get(up);
@@ -1154,7 +1153,7 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
return IRQ_HANDLED;
}
- spin_lock_irqsave(&port->lock, flags);
+ spin_lock(&port->lock);
status = serial_port_in(port, UART_LSR);
@@ -1179,7 +1178,8 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
}
}
- uart_unlock_and_check_sysrq(port, flags);
+ uart_unlock_and_check_sysrq(port);
+
serial8250_rpm_put(up);
return 1;
}
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 9019f8f626bb..d45dab1ab316 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1879,14 +1879,13 @@ static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
{
unsigned char status;
- unsigned long flags;
struct uart_8250_port *up = up_to_u8250p(port);
bool skip_rx = false;
if (iir & UART_IIR_NO_INT)
return 0;
- spin_lock_irqsave(&port->lock, flags);
+ spin_lock(&port->lock);
status = serial_port_in(port, UART_LSR);
@@ -1912,7 +1911,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
(up->ier & UART_IER_THRI))
serial8250_tx_chars(up);
- uart_unlock_and_check_sysrq(port, flags);
+ uart_unlock_and_check_sysrq(port);
+
return 1;
}
EXPORT_SYMBOL_GPL(serial8250_handle_irq);
diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 0d85b55ea823..00bb88a71606 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -818,7 +818,6 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
u32 s_irq_status;
u32 geni_status;
struct uart_port *uport = dev;
- unsigned long flags;
bool drop_rx = false;
struct tty_port *tport = &uport->state->port;
struct qcom_geni_serial_port *port = to_dev_port(uport, uport);
@@ -826,7 +825,8 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
if (uport->suspended)
return IRQ_NONE;
- spin_lock_irqsave(&uport->lock, flags);
+ spin_lock(&uport->lock);
+
m_irq_status = readl(uport->membase + SE_GENI_M_IRQ_STATUS);
s_irq_status = readl(uport->membase + SE_GENI_S_IRQ_STATUS);
geni_status = readl(uport->membase + SE_GENI_STATUS);
@@ -861,7 +861,7 @@ static irqreturn_t qcom_geni_serial_isr(int isr, void *dev)
qcom_geni_serial_handle_rx(uport, drop_rx);
out_unlock:
- uart_unlock_and_check_sysrq(uport, flags);
+ uart_unlock_and_check_sysrq(uport);
return IRQ_HANDLED;
}
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index e1b684e33841..d7ed00f1594e 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -500,19 +500,19 @@ static inline int uart_prepare_sysrq_char(struct uart_port *port, unsigned int c
return 0;
}
-static inline void uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
+static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
{
int sysrq_ch;
if (!port->has_sysrq) {
- spin_unlock_irqrestore(&port->lock, irqflags);
+ spin_unlock(&port->lock);
return;
}
sysrq_ch = port->sysrq_ch;
port->sysrq_ch = 0;
- spin_unlock_irqrestore(&port->lock, irqflags);
+ spin_unlock(&port->lock);
if (sysrq_ch)
handle_sysrq(sysrq_ch);
@@ -526,9 +526,9 @@ static inline int uart_prepare_sysrq_char(struct uart_port *port, unsigned int c
{
return 0;
}
-static inline void uart_unlock_and_check_sysrq(struct uart_port *port, unsigned long irqflags)
+static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
{
- spin_unlock_irqrestore(&port->lock, irqflags);
+ spin_unlock(&port->lock);
}
#endif /* CONFIG_MAGIC_SYSRQ_SERIAL */
--
2.26.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 2/3] serial: stm32: fix threaded interrupt handling
2021-04-16 14:05 [PATCH 0/3] serial: sysrq cleanup and stm32 fixes Johan Hovold
2021-04-16 14:05 ` [PATCH 1/3] serial: do not restore interrupt state in sysrq helper Johan Hovold
@ 2021-04-16 14:05 ` Johan Hovold
2021-04-16 14:19 ` Johan Hovold
` (2 more replies)
2021-04-16 14:05 ` [PATCH 3/3] serial: stm32: defer sysrq processing Johan Hovold
2 siblings, 3 replies; 8+ messages in thread
From: Johan Hovold @ 2021-04-16 14:05 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, dillon.minfei,
Erwan Le Ray, linux-serial, linux-kernel, Johan Hovold, stable,
Alexandre TORGUE, Gerald Baeza
When DMA is enabled the receive handler runs in a threaded handler, but
the primary handler up until very recently neither disabled interrupts
in the device or used IRQF_ONESHOT. This would lead to a deadlock if an
interrupt comes in while the threaded receive handler is running under
the port lock.
Commit ad7676812437 ("serial: stm32: fix a deadlock condition with
wakeup event") claimed to fix an unrelated deadlock, but unfortunately
also disabled interrupts in the threaded handler. While this prevents
the deadlock mentioned in the previous paragraph it also defeats the
purpose of using a threaded handler in the first place.
Fix this by making the interrupt one-shot and not disabling interrupts
in the threaded handler.
Note that (receive) DMA must not be used for a console port as the
threaded handler could be interrupted while holding the port lock,
something which could lead to a deadlock in case an interrupt handler
ends up calling printk.
Fixes: ad7676812437 ("serial: stm32: fix a deadlock condition with wakeup event")
Fixes: 3489187204eb ("serial: stm32: adding dma support")
Cc: stable@vger.kernel.org # 4.9
Cc: Alexandre TORGUE <alexandre.torgue@st.com>
Cc: Gerald Baeza <gerald.baeza@st.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/serial/stm32-usart.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 4d277804c63e..3524ed2c0c73 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -214,14 +214,11 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
struct tty_port *tport = &port->state->port;
struct stm32_port *stm32_port = to_stm32_port(port);
const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
- unsigned long c, flags;
+ unsigned long c;
u32 sr;
char flag;
- if (threaded)
- spin_lock_irqsave(&port->lock, flags);
- else
- spin_lock(&port->lock);
+ spin_lock(&port->lock);
while (stm32_usart_pending_rx(port, &sr, &stm32_port->last_res,
threaded)) {
@@ -278,10 +275,7 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
uart_insert_char(port, sr, USART_SR_ORE, c, flag);
}
- if (threaded)
- spin_unlock_irqrestore(&port->lock, flags);
- else
- spin_unlock(&port->lock);
+ spin_unlock(&port->lock);
tty_flip_buffer_push(tport);
}
@@ -667,7 +661,8 @@ static int stm32_usart_startup(struct uart_port *port)
ret = request_threaded_irq(port->irq, stm32_usart_interrupt,
stm32_usart_threaded_interrupt,
- IRQF_NO_SUSPEND, name, port);
+ IRQF_ONESHOT | IRQF_NO_SUSPEND,
+ name, port);
if (ret)
return ret;
@@ -1156,6 +1151,13 @@ static int stm32_usart_of_dma_rx_probe(struct stm32_port *stm32port,
struct dma_async_tx_descriptor *desc = NULL;
int ret;
+ /*
+ * Using DMA and threaded handler for the console could lead to
+ * deadlocks.
+ */
+ if (uart_console(port))
+ return -ENODEV;
+
/* Request DMA RX channel */
stm32port->rx_ch = dma_request_slave_channel(dev, "rx");
if (!stm32port->rx_ch) {
--
2.26.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH 3/3] serial: stm32: defer sysrq processing
2021-04-16 14:05 [PATCH 0/3] serial: sysrq cleanup and stm32 fixes Johan Hovold
2021-04-16 14:05 ` [PATCH 1/3] serial: do not restore interrupt state in sysrq helper Johan Hovold
2021-04-16 14:05 ` [PATCH 2/3] serial: stm32: fix threaded interrupt handling Johan Hovold
@ 2021-04-16 14:05 ` Johan Hovold
2021-04-22 9:36 ` Valentin CARON - foss
2 siblings, 1 reply; 8+ messages in thread
From: Johan Hovold @ 2021-04-16 14:05 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, dillon.minfei,
Erwan Le Ray, linux-serial, linux-kernel, Johan Hovold
Use the uart_unlock_and_check_sysrq() helper to defer sysrq processing
until receive processing is done and the port lock has been released.
This allows cleaning up the console_write() implementation by not having
to work around the recursive sysrq case (by dropping locking completely)
and also makes the console code work with PREEMPT_RT by no longer
relying on local_irq_save().
Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/tty/serial/stm32-usart.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 3524ed2c0c73..24a1dfe7058b 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -270,12 +270,12 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
}
}
- if (uart_handle_sysrq_char(port, c))
+ if (uart_prepare_sysrq_char(port, c))
continue;
uart_insert_char(port, sr, USART_SR_ORE, c, flag);
}
- spin_unlock(&port->lock);
+ uart_unlock_and_check_sysrq(port);
tty_flip_buffer_push(tport);
}
@@ -1430,13 +1430,10 @@ static void stm32_usart_console_write(struct console *co, const char *s,
u32 old_cr1, new_cr1;
int locked = 1;
- local_irq_save(flags);
- if (port->sysrq)
- locked = 0;
- else if (oops_in_progress)
- locked = spin_trylock(&port->lock);
+ if (oops_in_progress)
+ locked = spin_trylock_irqsave(&port->lock, flags);
else
- spin_lock(&port->lock);
+ spin_lock_irqsave(&port->lock, flags);
/* Save and disable interrupts, enable the transmitter */
old_cr1 = readl_relaxed(port->membase + ofs->cr1);
@@ -1450,8 +1447,7 @@ static void stm32_usart_console_write(struct console *co, const char *s,
writel_relaxed(old_cr1, port->membase + ofs->cr1);
if (locked)
- spin_unlock(&port->lock);
- local_irq_restore(flags);
+ spin_unlock_irqrestore(&port->lock, flags);
}
static int stm32_usart_console_setup(struct console *co, char *options)
--
2.26.3
^ permalink raw reply related [flat|nested] 8+ messages in thread