diff options
Diffstat (limited to 'drivers/tty/serial/serial_core.c')
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 40 |
1 files changed, 30 insertions, 10 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 53e6db8b0330..55ed4c66f77f 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -141,6 +141,9 @@ static void uart_start(struct tty_struct *tty) struct uart_port *port; unsigned long flags; + if (!state) + return; + port = uart_port_lock(state, flags); __uart_start(tty); uart_port_unlock(port, flags); @@ -195,10 +198,15 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state, if (!state->xmit.buf) { state->xmit.buf = (unsigned char *) page; uart_circ_clear(&state->xmit); + uart_port_unlock(uport, flags); } else { + uart_port_unlock(uport, flags); + /* + * Do not free() the page under the port lock, see + * uart_shutdown(). + */ free_page(page); } - uart_port_unlock(uport, flags); retval = uport->ops->startup(uport); if (retval == 0) { @@ -258,6 +266,7 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state) struct uart_port *uport = uart_port_check(state); struct tty_port *port = &state->port; unsigned long flags = 0; + char *xmit_buf = NULL; /* * Set the TTY IO error marker @@ -288,14 +297,18 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state) tty_port_set_suspended(port, 0); /* - * Free the transmit buffer page. + * Do not free() the transmit buffer page under the port lock since + * this can create various circular locking scenarios. For instance, + * console driver may need to allocate/free a debug object, which + * can endup in printk() recursion. */ uart_port_lock(state, flags); - if (state->xmit.buf) { - free_page((unsigned long)state->xmit.buf); - state->xmit.buf = NULL; - } + xmit_buf = state->xmit.buf; + state->xmit.buf = NULL; uart_port_unlock(uport, flags); + + if (xmit_buf) + free_page((unsigned long)xmit_buf); } /** @@ -530,10 +543,12 @@ static int uart_put_char(struct tty_struct *tty, unsigned char c) int ret = 0; circ = &state->xmit; - if (!circ->buf) + port = uart_port_lock(state, flags); + if (!circ->buf) { + uart_port_unlock(port, flags); return 0; + } - port = uart_port_lock(state, flags); if (port && uart_circ_chars_free(circ) != 0) { circ->buf[circ->head] = c; circ->head = (circ->head + 1) & (UART_XMIT_SIZE - 1); @@ -566,11 +581,13 @@ static int uart_write(struct tty_struct *tty, return -EL3HLT; } + port = uart_port_lock(state, flags); circ = &state->xmit; - if (!circ->buf) + if (!circ->buf) { + uart_port_unlock(port, flags); return 0; + } - port = uart_port_lock(state, flags); while (port) { c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE); if (count < c) @@ -703,6 +720,9 @@ static void uart_unthrottle(struct tty_struct *tty) struct uart_port *port; upstat_t mask = 0; + if (!state) + return; + port = uart_port_ref(state); if (!port) return; |