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| author | Yang Yingliang <yangyingliang@huawei.com> | 2022-12-05 16:04:34 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-01-19 17:26:31 +0100 |
| commit | 25d5648802f12ae486076ceca5d7ddf1fef792b2 (patch) | |
| tree | 64b803732e76f46804dd448149b9fde901619b30 /drivers/w1 | |
| parent | 2efb6edd52dc50273f5e68ad863dd1b1fb2f2d1c (diff) | |
| download | lwn-25d5648802f12ae486076ceca5d7ddf1fef792b2.tar.gz lwn-25d5648802f12ae486076ceca5d7ddf1fef792b2.zip | |
w1: fix deadloop in __w1_remove_master_device()
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>
Diffstat (limited to 'drivers/w1')
| -rw-r--r-- | drivers/w1/w1.c | 2 | ||||
| -rw-r--r-- | 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); |