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Content preview: From: Thomas Gleixner When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel conso [...] Content analysis details: (-1.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [2a0a:51c0:0:12e:550:0:0:1 listed in] [list.dnswl.org] 0.6 INVALID_DATE_TZ_ABSURD Invalid Date: header (timezone does not exist) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org From: Thomas Gleixner When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel console. So far this has been ignored and the printk output is based on the principle of hope. The rework of the console infrastructure which aims to support threaded and atomic consoles, requires to mark sections which modify the UART registers as unsafe. This allows the atomic write function to make informed decisions and eventually to restore operational state. It also allows to prevent the regular UART code from modifying UART registers while printk output is in progress. All modifications of UART registers are guarded by the UART port lock, which provides an obvious synchronization point with the console infrastructure. To avoid adding this functionality to all UART drivers, wrap the spin_[un]lock*() invocations for uart_port::lock into helper functions which just contain the spin_[un]lock*() invocations for now. In a subsequent step these helpers will gain the console synchronization mechanisms. Converted with coccinelle. No functional change. Signed-off-by: Thomas Gleixner --- drivers/tty/serial/arc_uart.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c index ad4ae19b6ce3..1aa5b2b49c26 100644 --- a/drivers/tty/serial/arc_uart.c +++ b/drivers/tty/serial/arc_uart.c @@ -279,9 +279,9 @@ static irqreturn_t arc_serial_isr(int irq, void *dev_id) if (status & RXIENB) { /* already in ISR, no need of xx_irqsave */ - spin_lock(&port->lock); + uart_port_lock(port); arc_serial_rx_chars(port, status); - spin_unlock(&port->lock); + uart_port_unlock(port); } if ((status & TXIENB) && (status & TXEMPTY)) { @@ -291,12 +291,12 @@ static irqreturn_t arc_serial_isr(int irq, void *dev_id) */ UART_TX_IRQ_DISABLE(port); - spin_lock(&port->lock); + uart_port_lock(port); if (!uart_tx_stopped(port)) arc_serial_tx_chars(port); - spin_unlock(&port->lock); + uart_port_unlock(port); } return IRQ_HANDLED; @@ -366,7 +366,7 @@ arc_serial_set_termios(struct uart_port *port, struct ktermios *new, uartl = hw_val & 0xFF; uarth = (hw_val >> 8) & 0xFF; - spin_lock_irqsave(&port->lock, flags); + uart_port_lock_irqsave(port, &flags); UART_ALL_IRQ_DISABLE(port); @@ -391,7 +391,7 @@ arc_serial_set_termios(struct uart_port *port, struct ktermios *new, uart_update_timeout(port, new->c_cflag, baud); - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); } static const char *arc_serial_type(struct uart_port *port) @@ -521,9 +521,9 @@ static void arc_serial_console_write(struct console *co, const char *s, struct uart_port *port = &arc_uart_ports[co->index].port; unsigned long flags; - spin_lock_irqsave(&port->lock, flags); + uart_port_lock_irqsave(port, &flags); uart_console_write(port, s, count, arc_serial_console_putchar); - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); } static struct console arc_console = {