Hi, guys, Recently, we have met fake interrupt issue when using UIO as our vpu driver in mulit-instances case, the issue can be described as below:
In multi-instances case, we use vpu_lock(semaphore) to implement the mutually exclusive access to the device, each instace open uio device once and will be associated with a fd and its own uio_listener, we use poll to wait for the hardware interrupt. So let's assume that there are two instances, A and B, their uio_listener->event_count and idev->event are all 0 at the beginning, then A get the vpu_lock and start to work, it will block at poll()(because listener->event_count == idev->count) until H/W interrupt happens (atomic_inc(&idev->event)), after it releases vpu_lock, B will get the lock and start to work, however, its poll will return immediately because B's uio_listener->event_count is 0 while idev->event has been 1, that's how the fake interrupt happens. Our proposal: Add new uio_sync_event(struct uio_listener *listener) function in uio,c, so that we can call it directly when we want to sync the event count. Xiaolong Ye (1): uio: add uio_event_sync interface drivers/uio/uio.c | 12 ++++++++++++ include/linux/uio_driver.h | 1 + 2 files changed, 13 insertions(+) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
