Trying to write console output from within the serial console driver while the port->lock is held causes recursive deadlock: CPU 0 spin_lock_irqsave(&port->lock) printk() console_unlock() call_console_drivers() serial8250_console_write() spin_lock_irqsave(&port->lock) ** DEADLOCK ** The 8250_dw i/o accessors try to write a console error message if the LCR workaround was unsuccessful. When the port->lock is already held (eg., when called from serial8250_set_termios()), this deadlocks. Make the error message a FIXME until a general solution is devised.
Unified · Split
| @@ -119,7 +119,10 @@ static void dw8250_serial_out(struct uart_port *p, int offset, int value) · 118 unmodified lines | ||
| 119 | 119 | dw8250_force_idle(p); |
| 120 | 120 | writeb(value, p->membase + (UART_LCR << p->regshift)); |
| 121 | 121 | } |
| 122 | − dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 122 | + /* | |
| 123 | + * FIXME: this deadlocks if port->lock is already held | |
| 124 | + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 125 | + */ | |
| 123 | 126 | } |
| 124 | 127 | } |
| 125 | 128 | |
| @@ -163,7 +166,10 @@ static void dw8250_serial_outq(struct uart_port *p, int offset, int value) · 37 unmodified lines | ||
| 163 | 166 | __raw_writeq(value & 0xff, |
| 164 | 167 | p->membase + (UART_LCR << p->regshift)); |
| 165 | 168 | } |
| 166 | − dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 169 | + /* | |
| 170 | + * FIXME: this deadlocks if port->lock is already held | |
| 171 | + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 172 | + */ | |
| 167 | 173 | } |
| 168 | 174 | } |
| 169 | 175 | #endif /* CONFIG_64BIT */ |
| @@ -187,7 +193,10 @@ static void dw8250_serial_out32(struct uart_port *p, int offset, int value) · 17 unmodified lines | ||
| 187 | 193 | dw8250_force_idle(p); |
| 188 | 194 | writel(value, p->membase + (UART_LCR << p->regshift)); |
| 189 | 195 | } |
| 190 | − dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 196 | + /* | |
| 197 | + * FIXME: this deadlocks if port->lock is already held | |
| 198 | + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); | |
| 199 | + */ | |
| 191 | 200 | } |
| 192 | 201 | } |
| 193 | 202 | |