From 25d5648802f12ae486076ceca5d7ddf1fef792b2 Mon Sep 17 00:00:00 2001 From: Yang Yingliang Date: Mon, 5 Dec 2022 16:04:34 +0800 Subject: 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 Link: https://lore.kernel.org/r/20221205080434.3149205-1-yangyingliang@huawei.com Signed-off-by: Greg Kroah-Hartman --- drivers/w1/w1.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/w1/w1.c') 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) { -- cgit v1.2.3 From 36225a7c72e9e3e1ce4001b6ce72849f5c9a2d3b Mon Sep 17 00:00:00 2001 From: Yang Yingliang Date: Mon, 5 Dec 2022 18:15:58 +0800 Subject: w1: fix WARNING after calling w1_process() I got the following WARNING message while removing driver(ds2482): ------------[ cut here ]------------ do not call blocking ops when !TASK_RUNNING; state=1 set at [<000000002d50bfb6>] w1_process+0x9e/0x1d0 [wire] WARNING: CPU: 0 PID: 262 at kernel/sched/core.c:9817 __might_sleep+0x98/0xa0 CPU: 0 PID: 262 Comm: w1_bus_master1 Tainted: G N 6.1.0-rc3+ #307 RIP: 0010:__might_sleep+0x98/0xa0 Call Trace: exit_signals+0x6c/0x550 do_exit+0x2b4/0x17e0 kthread_exit+0x52/0x60 kthread+0x16d/0x1e0 ret_from_fork+0x1f/0x30 The state of task is set to TASK_INTERRUPTIBLE in loop in w1_process(), set it to TASK_RUNNING when it breaks out of the loop to avoid the warning. Fixes: 3c52e4e62789 ("W1: w1_process, block or sleep") Signed-off-by: Yang Yingliang Link: https://lore.kernel.org/r/20221205101558.3599162-1-yangyingliang@huawei.com Signed-off-by: Greg Kroah-Hartman --- drivers/w1/w1.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/w1/w1.c') diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c index 8b35fae4cd61..4a2ddf730a3a 100644 --- a/drivers/w1/w1.c +++ b/drivers/w1/w1.c @@ -1195,8 +1195,10 @@ int w1_process(void *data) */ mutex_unlock(&dev->list_mutex); - if (kthread_should_stop()) + if (kthread_should_stop()) { + __set_current_state(TASK_RUNNING); break; + } /* Only sleep when the search is active. */ if (dev->search_count) { -- cgit v1.2.3