The driver may sleep with holding a spinlock.
The function call paths (from bottom to top) in Linux-4.16 are:
[FUNC] schedule
kernel/locking/rtmutex.c, 1223:
schedule in rt_mutex_handle_deadlock
kernel/locking/rtmutex.c, 1273:
rt_mutex_handle_deadlock in rt_mutex_slowlock
kernel/locking/rtmutex.c, 1249:
_raw_spin_lock_irqsave in rt_mutex_slowlock
To fix the bug, the spinlock is released before the loop of schedule()
This is found by my static analysis tool (DSAC).
Signed-off-by: Jia-Ju Bai <baijiaju1...@gmail.com>
---
v2:
* Release the spinlock before the loop, instead of v1 that releases the
spinlock before schedule() and then acquires the spinlock again.
Thank Steven for good advice.
---
kernel/locking/rtmutex.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 2823d4163a37..8f25a289abe8 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1205,7 +1205,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
}
static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
- struct rt_mutex_waiter *w)
+ struct rt_mutex_waiter *w, struct rt_mutex
*lock)
{
/*
* If the result is not -EDEADLOCK or the caller requested
@@ -1218,6 +1218,8 @@ static void rt_mutex_handle_deadlock(int res, int
detect_deadlock,
* Yell lowdly and stop the task right here.
*/
rt_mutex_print_deadlock(w);
+ /* We're not going anywhere, release the wait_lock */
+ raw_spin_unlock_irq(&lock->wait_lock);
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
schedule();
@@ -1269,7 +1271,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
if (unlikely(ret)) {
__set_current_state(TASK_RUNNING);
remove_waiter(lock, &waiter);
- rt_mutex_handle_deadlock(ret, chwalk, &waiter);
+ rt_mutex_handle_deadlock(ret, chwalk, &waiter, lock);
}
/*
--
2.17.0
