3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Darren Hart <[email protected]> commit 2588aba002d14e938c2f56d299ecf3e7ce1302a5 upstream. pch_uart_interrupt() takes priv->port.lock which leads to two recursive spinlock calls if low_latency==1 or CONFIG_PREEMPT_RT_FULL=y (one otherwise): pch_uart_interrupt spin_lock_irqsave(priv->port.lock, flags) case PCH_UART_IID_RDR_TO (data ready) handle_rx_to push_rx tty_port_tty_get spin_lock_irqsave(&port->lock, flags) <--- already hold this lock ... tty_flip_buffer_push ... flush_to_ldisc spin_lock_irqsave(&tty->buf.lock) spin_lock_irqsave(&tty->buf.lock) disc->ops->receive_buf(tty, char_buf) n_tty_receive_buf tty->ops->flush_chars() uart_flush_chars uart_start spin_lock_irqsave(&port->lock) <--- already hold this lock Avoid this by using a dedicated lock to protect the eg20t_port structure and IO access to its membase. This is more consistent with the 8250 driver. Ensure priv->lock is always take prior to priv->port.lock when taken at the same time. V2: Remove inadvertent whitespace change. V3: Account for oops_in_progress for the private lock in pch_console_write(). Note: Like the 8250 driver, if a printk is introduced anywhere inside the pch_console_write() critical section, the kernel will hang on a recursive spinlock on the private lock. The oops case is handled by using a trylock in the oops_in_progress case. Signed-off-by: Darren Hart <[email protected]> CC: Tomoya MORINAGA <[email protected]> CC: Feng Tang <[email protected]> CC: Alexander Stein <[email protected]> Acked-by: Alan Cox <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> [bwh: Backported to 3.2: - Adjust context - Drop changes to pch_console_write()] Signed-off-by: Ben Hutchings <[email protected]> --- drivers/tty/serial/pch_uart.c | 38 ++++++++++++++++++++++++++------------ 1 file changed, 26 insertions(+), 12 deletions(-) --- a/drivers/tty/serial/pch_uart.c +++ b/drivers/tty/serial/pch_uart.c @@ -236,6 +236,9 @@ struct eg20t_port { int tx_dma_use; void *rx_buf_virt; dma_addr_t rx_buf_dma; + + /* protect the eg20t_port private structure and io access to membase */ + spinlock_t lock; }; /** @@ -964,7 +967,7 @@ static irqreturn_t pch_uart_interrupt(in unsigned int iid; unsigned long flags; - spin_lock_irqsave(&priv->port.lock, flags); + spin_lock_irqsave(&priv->lock, flags); handled = 0; while ((iid = pch_uart_hal_get_iid(priv)) > 1) { switch (iid) { @@ -1017,7 +1020,7 @@ static irqreturn_t pch_uart_interrupt(in priv->int_dis_flag = 0; } - spin_unlock_irqrestore(&priv->port.lock, flags); + spin_unlock_irqrestore(&priv->lock, flags); return IRQ_RETVAL(handled); } @@ -1131,9 +1134,9 @@ static void pch_uart_break_ctl(struct ua unsigned long flags; priv = container_of(port, struct eg20t_port, port); - spin_lock_irqsave(&port->lock, flags); + spin_lock_irqsave(&priv->lock, flags); pch_uart_hal_set_break(priv, ctl); - spin_unlock_irqrestore(&port->lock, flags); + spin_unlock_irqrestore(&priv->lock, flags); } /* Grab any interrupt resources and initialise any low level driver state. */ @@ -1284,7 +1287,8 @@ static void pch_uart_set_termios(struct baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16); - spin_lock_irqsave(&port->lock, flags); + spin_lock_irqsave(&priv->lock, flags); + spin_lock(&port->lock); uart_update_timeout(port, termios->c_cflag, baud); rtn = pch_uart_hal_set_line(priv, baud, parity, bits, stb); @@ -1297,7 +1301,8 @@ static void pch_uart_set_termios(struct tty_termios_encode_baud_rate(termios, baud, baud); out: - spin_unlock_irqrestore(&port->lock, flags); + spin_unlock(&port->lock); + spin_unlock_irqrestore(&priv->lock, flags); } static const char *pch_uart_type(struct uart_port *port) @@ -1449,6 +1454,8 @@ static struct eg20t_port *pch_uart_init_ pci_enable_msi(pdev); pci_set_master(pdev); + spin_lock_init(&priv->lock); + iobase = pci_resource_start(pdev, 0); mapbase = pci_resource_start(pdev, 1); priv->mapbase = mapbase; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
