From: dillon min <dillon.min...@gmail.com>
This patch aims to fix two potential bug:
- no lock to protect uart register in this case
stm32_usart_threaded_interrupt()
spin_lock(&port->lock);
...
stm32_usart_receive_chars()
uart_handle_sysrq_char();
sysrq_function();
printk();
stm32_usart_console_write();
locked = 0; //since port->sysrq is not zero,
no lock to protect forward register
access.
- if add spin_trylock_irqsave() to protect uart register for sysrq = 1 case,
that might got recursive locking under UP.
So, use uart_prepare_sysrq_char(), uart_unlock_and_check_sysrq()
move sysrq handler position to irq/thread_d handler, just record
sysrq_ch in stm32_usart_receive_chars() by uart_prepare_sysrq_char()
delay the sysrq process to next interrupt handler.
new flow:
stm32_usart_threaded_interrupt()/stm32_usart_interrupt()
spin_lock_irqsave(&port->lock);
...
uart_unlock_and_check_sysrq();
spin_unlock_irqrestore();
handle_sysrq(sysrq_ch);
stm32_usart_threaded_interrupt()//stm32_usart_interrupt() return
Cc: Johan Hovold <jo...@kernel.org>
Cc: Alexandre Torgue <alexandre.tor...@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.st...@gmail.com>
Cc: Gerald Baeza <gerald.ba...@foss.st.com>
Cc: Erwan Le Ray <erwan.le...@foss.st.com>
Reported-by: kernel test robot <l...@intel.com>
Signed-off-by: dillon min <dillon.min...@gmail.com>
---
v3: add uart_prepare_sysrq_char(), uart_unlock_and_check_sysrq() to move
sysrq handler inside interrupt routinei to avoid recursive locking,
according to Johan Hovold suggestion, thanks.
drivers/tty/serial/stm32-usart.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index b3675cf25a69..981f50ec784e 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -271,7 +271,7 @@ 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);
}
@@ -457,9 +457,10 @@ static irqreturn_t stm32_usart_interrupt(int irq, void
*ptr)
struct uart_port *port = ptr;
struct stm32_port *stm32_port = to_stm32_port(port);
const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
+ unsigned long flags;
u32 sr;
- spin_lock(&port->lock);
+ spin_lock_irqsave(&port->lock, flags);
sr = readl_relaxed(port->membase + ofs->isr);
@@ -477,7 +478,7 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch))
stm32_usart_transmit_chars(port);
- spin_unlock(&port->lock);
+ uart_unlock_and_check_sysrq(port, flags);
if (stm32_port->rx_ch)
return IRQ_WAKE_THREAD;
@@ -489,13 +490,14 @@ static irqreturn_t stm32_usart_threaded_interrupt(int
irq, void *ptr)
{
struct uart_port *port = ptr;
struct stm32_port *stm32_port = to_stm32_port(port);
+ unsigned long flags;
- spin_lock(&port->lock);
+ spin_lock_irqsave(&port->lock, flags);
if (stm32_port->rx_ch)
stm32_usart_receive_chars(port, true);
- spin_unlock(&port->lock);
+ uart_unlock_and_check_sysrq(port, flags);
return IRQ_HANDLED;
}
@@ -1354,13 +1356,10 @@ 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);
@@ -1374,8 +1373,7 @@ 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)
--
2.7.4
