[SERIAL] Clean up serial locking when obtaining a reference to a port
The locking for the uart_port is over complicated, and can be simplified if we introduce a flag to indicate that a port is "dead" and will be removed. This also helps the validator because it removes a case of non-nested unlock ordering. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org>
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e0a515bc6a
commit
68ac64cd3f
2 changed files with 61 additions and 54 deletions
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@ -1500,20 +1500,18 @@ uart_block_til_ready(struct file *filp, struct uart_state *state)
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static struct uart_state *uart_get(struct uart_driver *drv, int line)
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{
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struct uart_state *state;
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int ret = 0;
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mutex_lock(&port_mutex);
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state = drv->state + line;
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if (mutex_lock_interruptible(&state->mutex)) {
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state = ERR_PTR(-ERESTARTSYS);
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goto out;
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ret = -ERESTARTSYS;
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goto err;
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}
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state->count++;
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if (!state->port) {
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state->count--;
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mutex_unlock(&state->mutex);
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state = ERR_PTR(-ENXIO);
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goto out;
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if (!state->port || state->port->flags & UPF_DEAD) {
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ret = -ENXIO;
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goto err_unlock;
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}
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if (!state->info) {
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@ -1531,15 +1529,17 @@ static struct uart_state *uart_get(struct uart_driver *drv, int line)
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tasklet_init(&state->info->tlet, uart_tasklet_action,
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(unsigned long)state);
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} else {
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state->count--;
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mutex_unlock(&state->mutex);
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state = ERR_PTR(-ENOMEM);
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ret = -ENOMEM;
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goto err_unlock;
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}
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}
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out:
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mutex_unlock(&port_mutex);
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return state;
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err_unlock:
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state->count--;
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mutex_unlock(&state->mutex);
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err:
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return ERR_PTR(ret);
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}
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/*
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@ -2085,45 +2085,6 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
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}
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}
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/*
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* This reverses the effects of uart_configure_port, hanging up the
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* port before removal.
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*/
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static void
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uart_unconfigure_port(struct uart_driver *drv, struct uart_state *state)
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{
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struct uart_port *port = state->port;
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struct uart_info *info = state->info;
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if (info && info->tty)
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tty_vhangup(info->tty);
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mutex_lock(&state->mutex);
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state->info = NULL;
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/*
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* Free the port IO and memory resources, if any.
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*/
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if (port->type != PORT_UNKNOWN)
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port->ops->release_port(port);
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/*
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* Indicate that there isn't a port here anymore.
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*/
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port->type = PORT_UNKNOWN;
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/*
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* Kill the tasklet, and free resources.
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*/
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if (info) {
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tasklet_kill(&info->tlet);
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kfree(info);
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}
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mutex_unlock(&state->mutex);
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}
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static struct tty_operations uart_ops = {
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.open = uart_open,
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.close = uart_close,
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@ -2270,6 +2231,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
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state = drv->state + port->line;
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mutex_lock(&port_mutex);
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mutex_lock(&state->mutex);
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if (state->port) {
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ret = -EINVAL;
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goto out;
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@ -2304,7 +2266,13 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
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port->cons && !(port->cons->flags & CON_ENABLED))
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register_console(port->cons);
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/*
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* Ensure UPF_DEAD is not set.
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*/
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port->flags &= ~UPF_DEAD;
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out:
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mutex_unlock(&state->mutex);
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mutex_unlock(&port_mutex);
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return ret;
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@ -2322,6 +2290,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
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int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
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{
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struct uart_state *state = drv->state + port->line;
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struct uart_info *info;
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BUG_ON(in_interrupt());
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@ -2331,12 +2300,49 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
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mutex_lock(&port_mutex);
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/*
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* Mark the port "dead" - this prevents any opens from
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* succeeding while we shut down the port.
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*/
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mutex_lock(&state->mutex);
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port->flags |= UPF_DEAD;
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mutex_unlock(&state->mutex);
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/*
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* Remove the devices from devfs
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*/
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tty_unregister_device(drv->tty_driver, port->line);
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uart_unconfigure_port(drv, state);
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info = state->info;
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if (info && info->tty)
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tty_vhangup(info->tty);
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/*
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* All users of this port should now be disconnected from
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* this driver, and the port shut down. We should be the
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* only thread fiddling with this port from now on.
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*/
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state->info = NULL;
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/*
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* Free the port IO and memory resources, if any.
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*/
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if (port->type != PORT_UNKNOWN)
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port->ops->release_port(port);
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/*
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* Indicate that there isn't a port here anymore.
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*/
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port->type = PORT_UNKNOWN;
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/*
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* Kill the tasklet, and free resources.
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*/
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if (info) {
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tasklet_kill(&info->tlet);
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kfree(info);
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}
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state->port = NULL;
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mutex_unlock(&port_mutex);
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@ -254,6 +254,7 @@ struct uart_port {
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#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
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#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
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#define UPF_BOOT_AUTOCONF ((__force upf_t) (1 << 28))
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#define UPF_DEAD ((__force upf_t) (1 << 30))
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#define UPF_IOREMAP ((__force upf_t) (1 << 31))
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#define UPF_CHANGE_MASK ((__force upf_t) (0x17fff))
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