diff options
author | Erwan Le Ray <erwan.leray@foss.st.com> | 2021-03-04 17:23:00 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-10 09:34:10 +0100 |
commit | ad7676812437a00a4c6be155fc17926069f99084 (patch) | |
tree | df710b54335c0cd32877ce3e47b0352ea47f47e6 /drivers/tty/serial/stm32-usart.c | |
parent | 25a8e7611da5513b388165661b17173c26e12c04 (diff) | |
download | linux-stable-ad7676812437a00a4c6be155fc17926069f99084.tar.gz linux-stable-ad7676812437a00a4c6be155fc17926069f99084.tar.bz2 linux-stable-ad7676812437a00a4c6be155fc17926069f99084.zip |
serial: stm32: fix a deadlock condition with wakeup event
Deadlock issue is seen when enabling CONFIG_PROVE_LOCKING=Y, and uart
console as wakeup source. Deadlock occurs when resuming from low power
mode if system is waked up via usart console.
The deadlock is triggered 100% when also disabling console suspend prior
to go to suspend.
Simplified call stack, deadlock condition:
- stm32_console_write <-- spin_lock already held
- print_circular_bug
- pm_wakeup_dev_event <-- triggers lockdep as seen above
- stm32_receive_chars
- stm32_interrupt <-- wakeup via uart console, takes the lock
So, revisit spin_lock in stm32-usart driver:
- there is no need to hold the lock to access ICR (atomic clear of status
flags)
- only hold the lock inside stm32_receive_chars() routine (no need to
call pm_wakeup_dev_event with lock held)
- keep stm32_transmit_chars() routine called with lock held
Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20210304162308.8984-6-erwan.leray@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/stm32-usart.c')
-rw-r--r-- | drivers/tty/serial/stm32-usart.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 223cec70c57c..370141445780 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -214,13 +214,18 @@ 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; + unsigned long c, flags; u32 sr; char flag; if (irqd_is_wakeup_set(irq_get_irq_data(port->irq))) pm_wakeup_event(tport->tty->dev, 0); + if (threaded) + spin_lock_irqsave(&port->lock, flags); + else + spin_lock(&port->lock); + while (stm32_usart_pending_rx(port, &sr, &stm32_port->last_res, threaded)) { sr |= USART_SR_DUMMY_RX; @@ -276,9 +281,12 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded) uart_insert_char(port, sr, USART_SR_ORE, c, flag); } - spin_unlock(&port->lock); + if (threaded) + spin_unlock_irqrestore(&port->lock, flags); + else + spin_unlock(&port->lock); + tty_flip_buffer_push(tport); - spin_lock(&port->lock); } static void stm32_usart_tx_dma_complete(void *arg) @@ -459,8 +467,6 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs; u32 sr; - spin_lock(&port->lock); - sr = readl_relaxed(port->membase + ofs->isr); if ((sr & USART_SR_RTOF) && ofs->icr != UNDEF_REG) @@ -474,10 +480,11 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr) if ((sr & USART_SR_RXNE) && !(stm32_port->rx_ch)) stm32_usart_receive_chars(port, false); - if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) + if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) { + spin_lock(&port->lock); stm32_usart_transmit_chars(port); - - spin_unlock(&port->lock); + spin_unlock(&port->lock); + } if (stm32_port->rx_ch) return IRQ_WAKE_THREAD; @@ -490,13 +497,9 @@ 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); - spin_lock(&port->lock); - if (stm32_port->rx_ch) stm32_usart_receive_chars(port, true); - spin_unlock(&port->lock); - return IRQ_HANDLED; } |