On Mon, Dec 15, 2025 at 10:49 AM Arnd Bergmann arnd@arndb.de wrote:
Is it always enough to wake up only one waiter? From your description it sounds like it might need wake_up_interruptible_all() instead, but I may be misunderstanding the issue.
Ah, I'm just not familiar with waitqueues, so that is very possible. I based it on out_intr(), which also only does a wake_up_interruptible(). So either this is enough, or we need a wholesale replacement of wake ups? :(
Nothing in the virtio console prevents a third thread from entering the fray and also getting stuck as far as I can tell.
- Thread A: write(): fill up vq, enter waitqueue - Thread B: write(): vq is full, enter waitqueue - Thread C: poll(): consume used buffers - vring_interrupt() dropped, both A and B stuck
Is there other locking going on in the virtio layer or somewhere else that would prevent concurrent write?
Best Lorenz