[PATCH 1/30] W1: fix deadlocks and remove w1_control_thread

Evgeniy Polyakov
2008-07-11T13:54:41Z

w1_control_thread was removed which would wake up every second
and process newly registered family codes and complete some final
cleanup for a removed master. Those routines were moved to the
threads that were previously requesting those operations. A new
function w1_reconnect_slaves takes care of reconnecting existing slave
devices when a new family code is registered or removed. The removal
case was missing and would cause a deadlock waiting for the family
code reference count to decrease, which will now happen. A problem
with registering a family code was fixed. A slave device would be
unattached if it wasn't yet claimed, then attached at the end of the
list, two unclaimed slaves would cause an infinite loop.

The struct w1_bus_master.search now takes a pointer to the struct
w1_master device to avoid searching for it, which would have caused a
lock ordering deadlock with the removal of w1_control_thread.

Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>

---
drivers/w1/masters/ds1wm.c | 6 +-
drivers/w1/w1.c | 146 ++++++++++---------------------------------
drivers/w1/w1.h | 19 +++++-
drivers/w1/w1_family.c | 6 ++-
drivers/w1/w1_family.h | 1 -
drivers/w1/w1_int.c | 12 ++++
drivers/w1/w1_io.c | 3 +-
7 files changed, 71 insertions(+), 122 deletions(-)

diff --git a/drivers/w1/masters/ds1wm.c b/drivers/w1/masters/ds1wm.c
index 10211e4..ea894bf 100644
--- a/drivers/w1/masters/ds1wm.c
+++ b/drivers/w1/masters/ds1wm.c
@@ -274,8 +274,8 @@ static u8 ds1wm_reset_bus(void *data)
return 0;
}

-static void ds1wm_search(void *data, u8 search_type,
- w1_slave_found_callback slave_found)
+static void ds1wm_search(void *data, struct w1_master *master_dev,
+ u8 search_type, w1_slave_found_callback slave_found)
{
struct ds1wm_data *ds1wm_data = data;
int i;
@@ -313,7 +313,7 @@ static void ds1wm_search(void *data, u8 search_type,
ds1wm_write_register(ds1wm_data, DS1WM_CMD, ~DS1WM_CMD_SRA);
ds1wm_reset(ds1wm_data);

- slave_found(ds1wm_data, rom_id);
+ slave_found(master_dev, rom_id);
}

/* --------------------------------------------------------------------- */
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 7293c9b..25640f6 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -46,20 +46,16 @@ MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");

static int w1_timeout = 10;
-static int w1_control_timeout = 1;
int w1_max_slave_count = 10;
int w1_max_slave_ttl = 10;

module_param_named(timeout, w1_timeout, int, 0);
-module_param_named(control_timeout, w1_control_timeout, int, 0);
module_param_named(max_slave_count, w1_max_slave_count, int, 0);
module_param_named(slave_ttl, w1_max_slave_ttl, int, 0);

DEFINE_MUTEX(w1_mlock);
LIST_HEAD(w1_masters);

-static struct task_struct *w1_control_thread;
-
static int w1_master_match(struct device *dev, struct device_driver *drv)
{
return 1;
@@ -390,7 +386,7 @@ int w1_create_master_attributes(struct w1_master *master)
return sysfs_create_group(&master->dev.kobj, &w1_master_defattr_group);
}

-static void w1_destroy_master_attributes(struct w1_master *master)
+void w1_destroy_master_attributes(struct w1_master *master)
{
sysfs_remove_group(&master->dev.kobj, &w1_master_defattr_group);
}
@@ -567,7 +563,7 @@ static int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
return 0;
}

-static void w1_slave_detach(struct w1_slave *sl)
+void w1_slave_detach(struct w1_slave *sl)
{
struct w1_netlink_msg msg;

@@ -591,24 +587,6 @@ static void w1_slave_detach(struct w1_slave *sl)
kfree(sl);
}

-static struct w1_master *w1_search_master(void *data)
-{
- struct w1_master *dev;
- int found = 0;
-
- mutex_lock(&w1_mlock);
- list_for_each_entry(dev, &w1_masters, w1_master_entry) {
- if (dev->bus_master->data == data) {
- found = 1;
- atomic_inc(&dev->refcnt);
- break;
- }
- }
- mutex_unlock(&w1_mlock);
-
- return (found)?dev:NULL;
-}
-
struct w1_master *w1_search_master_id(u32 id)
{
struct w1_master *dev;
@@ -656,34 +634,49 @@ struct w1_slave *w1_search_slave(struct w1_reg_num *id)
return (found)?sl:NULL;
}

-void w1_reconnect_slaves(struct w1_family *f)
+void w1_reconnect_slaves(struct w1_family *f, int attach)
{
+ struct w1_slave *sl, *sln;
struct w1_master *dev;

mutex_lock(&w1_mlock);
list_for_each_entry(dev, &w1_masters, w1_master_entry) {
- dev_dbg(&dev->dev, "Reconnecting slaves in %s into new family %02x.\n",
- dev->name, f->fid);
- set_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
+ dev_dbg(&dev->dev, "Reconnecting slaves in device %s "
+ "for family %02x.\n", dev->name, f->fid);
+ mutex_lock(&dev->mutex);
+ list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
+ /* If it is a new family, slaves with the default
+ * family driver and are that family will be
+ * connected. If the family is going away, devices
+ * matching that family are reconneced.
+ */
+ if ((attach && sl->family->fid == W1_FAMILY_DEFAULT
+ && sl->reg_num.family == f->fid) ||
+ (!attach && sl->family->fid == f->fid)) {
+ struct w1_reg_num rn;
+
+ memcpy(&rn, &sl->reg_num, sizeof(rn));
+ w1_slave_detach(sl);
+
+ w1_attach_slave_device(dev, &rn);
+ }
+ }
+ dev_dbg(&dev->dev, "Reconnecting slaves in device %s "
+ "has been finished.\n", dev->name);
+ mutex_unlock(&dev->mutex);
}
mutex_unlock(&w1_mlock);
}

-static void w1_slave_found(void *data, u64 rn)
+static void w1_slave_found(struct w1_master *dev, u64 rn)
{
int slave_count;
struct w1_slave *sl;
struct list_head *ent;
struct w1_reg_num *tmp;
- struct w1_master *dev;
u64 rn_le = cpu_to_le64(rn);

- dev = w1_search_master(data);
- if (!dev) {
- printk(KERN_ERR "Failed to find w1 master device for data %p, "
- "it is impossible.\n", data);
- return;
- }
+ atomic_inc(&dev->refcnt);

tmp = (struct w1_reg_num *) &rn;

@@ -785,76 +778,11 @@ void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb
if ( (desc_bit == last_zero) || (last_zero < 0))
last_device = 1;
desc_bit = last_zero;
- cb(dev->bus_master->data, rn);
+ cb(dev, rn);
}
}
}

-static int w1_control(void *data)
-{
- struct w1_slave *sl, *sln;
- struct w1_master *dev, *n;
- int have_to_wait = 0;
-
- set_freezable();
- while (!kthread_should_stop() || have_to_wait) {
- have_to_wait = 0;
-
- try_to_freeze();
- msleep_interruptible(w1_control_timeout * 1000);
-
- list_for_each_entry_safe(dev, n, &w1_masters, w1_master_entry) {
- if (!kthread_should_stop() && !dev->flags)
- continue;
- /*
- * Little race: we can create thread but not set the flag.
- * Get a chance for external process to set flag up.
- */
- if (!dev->initialized) {
- have_to_wait = 1;
- continue;
- }
-
- if (kthread_should_stop() || test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
- set_bit(W1_MASTER_NEED_EXIT, &dev->flags);
-
- mutex_lock(&w1_mlock);
- list_del(&dev->w1_master_entry);
- mutex_unlock(&w1_mlock);
-
- mutex_lock(&dev->mutex);
- list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
- w1_slave_detach(sl);
- }
- w1_destroy_master_attributes(dev);
- mutex_unlock(&dev->mutex);
- atomic_dec(&dev->refcnt);
- continue;
- }
-
- if (test_bit(W1_MASTER_NEED_RECONNECT, &dev->flags)) {
- dev_dbg(&dev->dev, "Reconnecting slaves in device %s.\n", dev->name);
- mutex_lock(&dev->mutex);
- list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
- if (sl->family->fid == W1_FAMILY_DEFAULT) {
- struct w1_reg_num rn;
-
- memcpy(&rn, &sl->reg_num, sizeof(rn));
- w1_slave_detach(sl);
-
- w1_attach_slave_device(dev, &rn);
- }
- }
- dev_dbg(&dev->dev, "Reconnecting slaves in device %s has been finished.\n", dev->name);
- clear_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
- mutex_unlock(&dev->mutex);
- }
- }
- }
-
- return 0;
-}
-
void w1_search_process(struct w1_master *dev, u8 search_type)
{
struct w1_slave *sl, *sln;
@@ -932,18 +860,13 @@ static int w1_init(void)
goto err_out_master_unregister;
}

- w1_control_thread = kthread_run(w1_control, NULL, "w1_control");
- if (IS_ERR(w1_control_thread)) {
- retval = PTR_ERR(w1_control_thread);
- printk(KERN_ERR "Failed to create control thread. err=%d\n",
- retval);
- goto err_out_slave_unregister;
- }
-
return 0;

+#if 0
+/* For undoing the slave register if there was a step after it. */
err_out_slave_unregister:
driver_unregister(&w1_slave_driver);
+#endif

err_out_master_unregister:
driver_unregister(&w1_master_driver);
@@ -959,13 +882,12 @@ static void w1_fini(void)
{
struct w1_master *dev;

+ /* Set netlink removal messages and some cleanup */
list_for_each_entry(dev, &w1_masters, w1_master_entry)
__w1_remove_master_device(dev);

w1_fini_netlink();

- kthread_stop(w1_control_thread);
-
driver_unregister(&w1_slave_driver);
driver_unregister(&w1_master_driver);
bus_unregister(&w1_bus_type);
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index f1df534..13e0ea8 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -77,7 +77,7 @@ struct w1_slave
struct completion released;
};

-typedef void (* w1_slave_found_callback)(void *, u64);
+typedef void (*w1_slave_found_callback)(struct w1_master *, u64);

/**
@@ -142,12 +142,14 @@ struct w1_bus_master
*/
u8 (*reset_bus)(void *);

- /** Really nice hardware can handles the different types of ROM search */
- void (*search)(void *, u8, w1_slave_found_callback);
+ /** Really nice hardware can handles the different types of ROM search
+ * w1_master* is passed to the slave found callback.
+ */
+ void (*search)(void *, struct w1_master *,
+ u8, w1_slave_found_callback);
};

#define W1_MASTER_NEED_EXIT 0
-#define W1_MASTER_NEED_RECONNECT 1

struct w1_master
{
@@ -181,12 +183,21 @@ struct w1_master
};

int w1_create_master_attributes(struct w1_master *);
+void w1_destroy_master_attributes(struct w1_master *master);
void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb);
void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb);
struct w1_slave *w1_search_slave(struct w1_reg_num *id);
void w1_search_process(struct w1_master *dev, u8 search_type);
struct w1_master *w1_search_master_id(u32 id);

+/* Disconnect and reconnect devices in the given family. Used for finding
+ * unclaimed devices after a family has been registered or releasing devices
+ * after a family has been unregistered. Set attach to 1 when a new family
+ * has just been registered, to 0 when it has been unregistered.
+ */
+void w1_reconnect_slaves(struct w1_family *f, int attach);
+void w1_slave_detach(struct w1_slave *sl);
+
u8 w1_triplet(struct w1_master *dev, int bdir);
void w1_write_8(struct w1_master *, u8);
int w1_reset_bus(struct w1_master *);
diff --git a/drivers/w1/w1_family.c b/drivers/w1/w1_family.c
index a3c95bd..8c35f9c 100644
--- a/drivers/w1/w1_family.c
+++ b/drivers/w1/w1_family.c
@@ -53,7 +53,8 @@ int w1_register_family(struct w1_family *newf)
}
spin_unlock(&w1_flock);

- w1_reconnect_slaves(newf);
+ /* check default devices against the new set of drivers */
+ w1_reconnect_slaves(newf, 1);

return ret;
}
@@ -77,6 +78,9 @@ void w1_unregister_family(struct w1_family *fent)

spin_unlock(&w1_flock);

+ /* deatch devices using this family code */
+ w1_reconnect_slaves(fent, 0);
+
while (atomic_read(&fent->refcnt)) {
printk(KERN_INFO "Waiting for family %u to become free: refcnt=%d.\n",
fent->fid, atomic_read(&fent->refcnt));
diff --git a/drivers/w1/w1_family.h b/drivers/w1/w1_family.h
index ef1e1da..296a87e 100644
--- a/drivers/w1/w1_family.h
+++ b/drivers/w1/w1_family.h
@@ -63,6 +63,5 @@ void __w1_family_get(struct w1_family *);
struct w1_family * w1_family_registered(u8);
void w1_unregister_family(struct w1_family *);
int w1_register_family(struct w1_family *);
-void w1_reconnect_slaves(struct w1_family *f);

#endif /* __W1_FAMILY_H */
diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c
index 6840dfe..ed32280 100644
--- a/drivers/w1/w1_int.c
+++ b/drivers/w1/w1_int.c
@@ -148,10 +148,22 @@ err_out_free_dev:
void __w1_remove_master_device(struct w1_master *dev)
{
struct w1_netlink_msg msg;
+ struct w1_slave *sl, *sln;

set_bit(W1_MASTER_NEED_EXIT, &dev->flags);
kthread_stop(dev->thread);

+ mutex_lock(&w1_mlock);
+ list_del(&dev->w1_master_entry);
+ mutex_unlock(&w1_mlock);
+
+ mutex_lock(&dev->mutex);
+ list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry)
+ w1_slave_detach(sl);
+ w1_destroy_master_attributes(dev);
+ mutex_unlock(&dev->mutex);
+ atomic_dec(&dev->refcnt);
+
while (atomic_read(&dev->refcnt)) {
dev_info(&dev->dev, "Waiting for %s to become free: refcnt=%d.\n",
dev->name, atomic_read(&dev->refcnt));
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 30b6fbf..0056ef6 100644
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -277,7 +277,8 @@ void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_cal
{
dev->attempts++;
if (dev->bus_master->search)
- dev->bus_master->search(dev->bus_master->data, search_type, cb);
+ dev->bus_master->search(dev->bus_master->data, dev,
+ search_type, cb);
else
w1_search(dev, search_type, cb);
}
--
1.4.4.4