From: Yang Yingliang yangyingliang@huawei.com
[ Upstream commit 25d5648802f12ae486076ceca5d7ddf1fef792b2 ]
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 yangyingliang@huawei.com Link: https://lore.kernel.org/r/20221205080434.3149205-1-yangyingliang@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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);