i2c-core: Use per-adapter userspace device lists

Using a single list for all userspace devices leads to a dead lock
on multiplexed buses in some circumstances (mux chip instantiated
from userspace). This is solved by using a separate list for each
bus segment.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Michael Lawnick <ml.lawnick@gmx.de>

1 files changed, 18 insertions, 16 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 5105126225c3..c2258a51fe0c 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -40,12 +40,11 @@
 #include "i2c-core.h"
 
 
-/* core_lock protects i2c_adapter_idr, userspace_devices, and guarantees
+/* core_lock protects i2c_adapter_idr, and guarantees
    that device detection, deletion of detected devices, and attach_adapter
    and detach_adapter calls are serialized */
 static DEFINE_MUTEX(core_lock);
 static DEFINE_IDR(i2c_adapter_idr);
-static LIST_HEAD(userspace_devices);
 
 static struct device_type i2c_client_type;
 static int i2c_check_addr(struct i2c_adapter *adapter, int addr);
@@ -542,9 +541,9 @@ i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
                 return -EEXIST;
 
         /* Keep track of the added device */
-        mutex_lock(&core_lock);
-        list_add_tail(&client->detected, &userspace_devices);
-        mutex_unlock(&core_lock);
+        i2c_lock_adapter(adap);
+        list_add_tail(&client->detected, &adap->userspace_clients);
+        i2c_unlock_adapter(adap);
         dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
                  info.type, info.addr);
 
@@ -583,9 +582,10 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
 
         /* Make sure the device was added through sysfs */
         res = -ENOENT;
-        mutex_lock(&core_lock);
-        list_for_each_entry_safe(client, next, &userspace_devices, detected) {
-                if (client->addr == addr && client->adapter == adap) {
+        i2c_lock_adapter(adap);
+        list_for_each_entry_safe(client, next, &adap->userspace_clients,
+                                 detected) {
+                if (client->addr == addr) {
                         dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",
                                  "delete_device", client->name, client->addr);
 
@@ -595,7 +595,7 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
                         break;
                 }
         }
-        mutex_unlock(&core_lock);
+        i2c_unlock_adapter(adap);
 
         if (res < 0)
                 dev_err(dev, "%s: Can't find device in list\n",
@@ -677,6 +677,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
         }
 
         rt_mutex_init(&adap->bus_lock);
+        INIT_LIST_HEAD(&adap->userspace_clients);
 
         /* Set default timeout to 1 second if not already set */
         if (adap->timeout == 0)
@@ -879,14 +880,15 @@ int i2c_del_adapter(struct i2c_adapter *adap)
                 return res;
 
         /* Remove devices instantiated from sysfs */
-        list_for_each_entry_safe(client, next, &userspace_devices, detected) {
-                if (client->adapter == adap) {
-                        dev_dbg(&adap->dev, "Removing %s at 0x%x\n",
-                                client->name, client->addr);
-                        list_del(&client->detected);
-                        i2c_unregister_device(client);
-                }
+        i2c_lock_adapter(adap);
+        list_for_each_entry_safe(client, next, &adap->userspace_clients,
+                                 detected) {
+                dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
+                        client->addr);
+                list_del(&client->detected);
+                i2c_unregister_device(client);
         }
+        i2c_unlock_adapter(adap);
 
         /* Detach any active clients. This can't fail, thus we do not
            checking the returned value. */