Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | YE Chengfeng <> | Subject | [PATCH v2 1/2] gpiolib: cdev: Fix &lr->wait.lock deadlock issue | Date | Mon, 26 Jun 2023 10:39:56 +0000 |
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linereq_put_event is called from both interrupt context (e.g., edge_irq_thread) and process context (process_hw_ts_thread). Therefore, interrupt should be disabled before acquiring lock &lr->wait.lock inside linereq_put_event to avoid deadlock when the lock is held in process context and edge_irq_thread comes.
Similarly, linereq_read_unlocked running in process context also acquies the same lock. It also need to disable interrupt otherwise deadlock could happen if the irq edge_irq_thread comes to execution while the lock is held.
Fix the two potential deadlock issues by spin_lock_bh() and spin_lock_irq() separately.
Fixes: 73e0341992b6 ("gpiolib: cdev: support edge detection for uAPI v2") Signed-off-by: Chengfeng Ye <cyeaa@connect.ust.hk> --- drivers/gpio/gpiolib-cdev.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index 0a33971c964c..f768d46bdea7 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -615,13 +615,13 @@ static void linereq_put_event(struct linereq *lr, { bool overflow = false; - spin_lock(&lr->wait.lock); + spin_lock_bh(&lr->wait.lock); if (kfifo_is_full(&lr->events)) { overflow = true; kfifo_skip(&lr->events); } kfifo_in(&lr->events, le, 1); - spin_unlock(&lr->wait.lock); + spin_unlock_bh(&lr->wait.lock); if (!overflow) wake_up_poll(&lr->wait, EPOLLIN); else @@ -1514,28 +1514,28 @@ static ssize_t linereq_read_unlocked(struct file *file, char __user *buf, return -EINVAL; do { - spin_lock(&lr->wait.lock); + spin_lock_irq(&lr->wait.lock); if (kfifo_is_empty(&lr->events)) { if (bytes_read) { - spin_unlock(&lr->wait.lock); + spin_unlock_irq(&lr->wait.lock); return bytes_read; } if (file->f_flags & O_NONBLOCK) { - spin_unlock(&lr->wait.lock); + spin_unlock_irq(&lr->wait.lock); return -EAGAIN; } - ret = wait_event_interruptible_locked(lr->wait, + ret = wait_event_interruptible_locked_irq(lr->wait, !kfifo_is_empty(&lr->events)); if (ret) { - spin_unlock(&lr->wait.lock); + spin_unlock_irq(&lr->wait.lock); return ret; } } ret = kfifo_out(&lr->events, &le, 1); - spin_unlock(&lr->wait.lock); + spin_unlock_irq(&lr->wait.lock); if (ret != 1) { /* * This should never happen - we were holding the -- 2.17.1 | ![\](/images/icornerr.gif) |