I got a deadloop report while doing device(ds2482) add/remove test:
[ 162.241881] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
[ 163.272251] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
[ 164.296157] w1_master_driver w1_bus_master1: Waiting for w1_bus_master1 to become free: refcnt=1.
...
__w1_remove_master_device() can't return, because the dev->refcnt is not zero.
w1_add_master_device() |
w1_alloc_dev() |
atomic_set(&dev->refcnt, 2) |
kthread_run() |
|__w1_remove_master_device()
| kthread_stop()
// KTHREAD_SHOULD_STOP is set, |
// threadfn(w1_process) won't be |
// called. |
kthread() |
| // refcnt will never be 0, it's deadloop.
| while (atomic_read(&dev->refcnt)) {...}
After calling w1_add_master_device(), w1_process() is not really
invoked, before w1_process() starting, if kthread_stop() is called
in __w1_remove_master_device(), w1_process() will never be called,
the refcnt can not be decreased, then it causes deadloop in remove
function because of non-zero refcnt.
We need to make sure w1_process() is really started, so move the
set refcnt into w1_process() to fix this problem.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Yang Yingliang <[email protected]>
---
drivers/w1/w1.c | 2 ++
drivers/w1/w1_int.c | 5 ++---
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index f2ae2e563dc5..8b35fae4cd61 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -1166,6 +1166,8 @@ int w1_process(void *data)
/* remainder if it woke up early */
unsigned long jremain = 0;
+ atomic_inc(&dev->refcnt);
+
for (;;) {
if (!jremain && dev->search_count) {
diff --git a/drivers/w1/w1_int.c b/drivers/w1/w1_int.c
index b3e1792d9c49..3a71c5eb2f83 100644
--- a/drivers/w1/w1_int.c
+++ b/drivers/w1/w1_int.c
@@ -51,10 +51,9 @@ static struct w1_master *w1_alloc_dev(u32 id, int slave_count, int slave_ttl,
dev->search_count = w1_search_count;
dev->enable_pullup = w1_enable_pullup;
- /* 1 for w1_process to decrement
- * 1 for __w1_remove_master_device to decrement
+ /* For __w1_remove_master_device to decrement
*/
- atomic_set(&dev->refcnt, 2);
+ atomic_set(&dev->refcnt, 1);
INIT_LIST_HEAD(&dev->slist);
INIT_LIST_HEAD(&dev->async_list);
--
2.25.1