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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2006-04-30 06:13:50 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2006-04-30 06:13:50 -0400
commit68ac64cd3fd89fdaa091701f6ab98a9065e9b1b5 (patch)
tree349dc1446bb52b87ce11f7ba2bb52d90679d3dd5 /drivers
parente0a515bc6a2188f02916e976f419a8640312e32a (diff)
[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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/serial/serial_core.c114
1 files changed, 60 insertions, 54 deletions
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index fcd7744c4253..aeb8153ccf24 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1500,20 +1500,18 @@ uart_block_til_ready(struct file *filp, struct uart_state *state)
1500static struct uart_state *uart_get(struct uart_driver *drv, int line) 1500static struct uart_state *uart_get(struct uart_driver *drv, int line)
1501{ 1501{
1502 struct uart_state *state; 1502 struct uart_state *state;
1503 int ret = 0;
1503 1504
1504 mutex_lock(&port_mutex);
1505 state = drv->state + line; 1505 state = drv->state + line;
1506 if (mutex_lock_interruptible(&state->mutex)) { 1506 if (mutex_lock_interruptible(&state->mutex)) {
1507 state = ERR_PTR(-ERESTARTSYS); 1507 ret = -ERESTARTSYS;
1508 goto out; 1508 goto err;
1509 } 1509 }
1510 1510
1511 state->count++; 1511 state->count++;
1512 if (!state->port) { 1512 if (!state->port || state->port->flags & UPF_DEAD) {
1513 state->count--; 1513 ret = -ENXIO;
1514 mutex_unlock(&state->mutex); 1514 goto err_unlock;
1515 state = ERR_PTR(-ENXIO);
1516 goto out;
1517 } 1515 }
1518 1516
1519 if (!state->info) { 1517 if (!state->info) {
@@ -1531,15 +1529,17 @@ static struct uart_state *uart_get(struct uart_driver *drv, int line)
1531 tasklet_init(&state->info->tlet, uart_tasklet_action, 1529 tasklet_init(&state->info->tlet, uart_tasklet_action,
1532 (unsigned long)state); 1530 (unsigned long)state);
1533 } else { 1531 } else {
1534 state->count--; 1532 ret = -ENOMEM;
1535 mutex_unlock(&state->mutex); 1533 goto err_unlock;
1536 state = ERR_PTR(-ENOMEM);
1537 } 1534 }
1538 } 1535 }
1539
1540 out:
1541 mutex_unlock(&port_mutex);
1542 return state; 1536 return state;
1537
1538 err_unlock:
1539 state->count--;
1540 mutex_unlock(&state->mutex);
1541 err:
1542 return ERR_PTR(ret);
1543} 1543}
1544 1544
1545/* 1545/*
@@ -2085,45 +2085,6 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
2085 } 2085 }
2086} 2086}
2087 2087
2088/*
2089 * This reverses the effects of uart_configure_port, hanging up the
2090 * port before removal.
2091 */
2092static void
2093uart_unconfigure_port(struct uart_driver *drv, struct uart_state *state)
2094{
2095 struct uart_port *port = state->port;
2096 struct uart_info *info = state->info;
2097
2098 if (info && info->tty)
2099 tty_vhangup(info->tty);
2100
2101 mutex_lock(&state->mutex);
2102
2103 state->info = NULL;
2104
2105 /*
2106 * Free the port IO and memory resources, if any.
2107 */
2108 if (port->type != PORT_UNKNOWN)
2109 port->ops->release_port(port);
2110
2111 /*
2112 * Indicate that there isn't a port here anymore.
2113 */
2114 port->type = PORT_UNKNOWN;
2115
2116 /*
2117 * Kill the tasklet, and free resources.
2118 */
2119 if (info) {
2120 tasklet_kill(&info->tlet);
2121 kfree(info);
2122 }
2123
2124 mutex_unlock(&state->mutex);
2125}
2126
2127static struct tty_operations uart_ops = { 2088static struct tty_operations uart_ops = {
2128 .open = uart_open, 2089 .open = uart_open,
2129 .close = uart_close, 2090 .close = uart_close,
@@ -2270,6 +2231,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
2270 state = drv->state + port->line; 2231 state = drv->state + port->line;
2271 2232
2272 mutex_lock(&port_mutex); 2233 mutex_lock(&port_mutex);
2234 mutex_lock(&state->mutex);
2273 if (state->port) { 2235 if (state->port) {
2274 ret = -EINVAL; 2236 ret = -EINVAL;
2275 goto out; 2237 goto out;
@@ -2304,7 +2266,13 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
2304 port->cons && !(port->cons->flags & CON_ENABLED)) 2266 port->cons && !(port->cons->flags & CON_ENABLED))
2305 register_console(port->cons); 2267 register_console(port->cons);
2306 2268
2269 /*
2270 * Ensure UPF_DEAD is not set.
2271 */
2272 port->flags &= ~UPF_DEAD;
2273
2307 out: 2274 out:
2275 mutex_unlock(&state->mutex);
2308 mutex_unlock(&port_mutex); 2276 mutex_unlock(&port_mutex);
2309 2277
2310 return ret; 2278 return ret;
@@ -2322,6 +2290,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *port)
2322int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port) 2290int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
2323{ 2291{
2324 struct uart_state *state = drv->state + port->line; 2292 struct uart_state *state = drv->state + port->line;
2293 struct uart_info *info;
2325 2294
2326 BUG_ON(in_interrupt()); 2295 BUG_ON(in_interrupt());
2327 2296
@@ -2332,11 +2301,48 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
2332 mutex_lock(&port_mutex); 2301 mutex_lock(&port_mutex);
2333 2302
2334 /* 2303 /*
2304 * Mark the port "dead" - this prevents any opens from
2305 * succeeding while we shut down the port.
2306 */
2307 mutex_lock(&state->mutex);
2308 port->flags |= UPF_DEAD;
2309 mutex_unlock(&state->mutex);
2310
2311 /*
2335 * Remove the devices from devfs 2312 * Remove the devices from devfs
2336 */ 2313 */
2337 tty_unregister_device(drv->tty_driver, port->line); 2314 tty_unregister_device(drv->tty_driver, port->line);
2338 2315
2339 uart_unconfigure_port(drv, state); 2316 info = state->info;
2317 if (info && info->tty)
2318 tty_vhangup(info->tty);
2319
2320 /*
2321 * All users of this port should now be disconnected from
2322 * this driver, and the port shut down. We should be the
2323 * only thread fiddling with this port from now on.
2324 */
2325 state->info = NULL;
2326
2327 /*
2328 * Free the port IO and memory resources, if any.
2329 */
2330 if (port->type != PORT_UNKNOWN)
2331 port->ops->release_port(port);
2332
2333 /*
2334 * Indicate that there isn't a port here anymore.
2335 */
2336 port->type = PORT_UNKNOWN;
2337
2338 /*
2339 * Kill the tasklet, and free resources.
2340 */
2341 if (info) {
2342 tasklet_kill(&info->tlet);
2343 kfree(info);
2344 }
2345
2340 state->port = NULL; 2346 state->port = NULL;
2341 mutex_unlock(&port_mutex); 2347 mutex_unlock(&port_mutex);
2342 2348