From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> mainline commit: c5cbdb76e8e33ce90fec2946e8eee7d71d68e57a 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 <tglx@xxxxxxxxxxxxx> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20230914183831.587273-3-john.ogness@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/serial_core.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index f1d5c0d1568c..3091c62ec37b 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -1035,14 +1035,14 @@ static inline void uart_unlock_and_check_sysrq(struct uart_port *port) u8 sysrq_ch; if (!port->has_sysrq) { - spin_unlock(&port->lock); + uart_port_unlock(port); return; } sysrq_ch = port->sysrq_ch; port->sysrq_ch = 0; - spin_unlock(&port->lock); + uart_port_unlock(port); if (sysrq_ch) handle_sysrq(sysrq_ch); @@ -1054,14 +1054,14 @@ static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port u8 sysrq_ch; if (!port->has_sysrq) { - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); return; } sysrq_ch = port->sysrq_ch; port->sysrq_ch = 0; - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); if (sysrq_ch) handle_sysrq(sysrq_ch); @@ -1077,12 +1077,12 @@ static inline int uart_prepare_sysrq_char(struct uart_port *port, u8 ch) } static inline void uart_unlock_and_check_sysrq(struct uart_port *port) { - spin_unlock(&port->lock); + uart_port_unlock(port); } static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port, unsigned long flags) { - spin_unlock_irqrestore(&port->lock, flags); + uart_port_unlock_irqrestore(port, flags); } #endif /* CONFIG_MAGIC_SYSRQ_SERIAL */ -- 2.39.2
